ci(INFRA-3593): Phase 1 — Namespace cache for Linux CI trial (MetaMask#29716)

## **Description**

INFRA-3593 Phase 1 — adds Namespace Cache Volumes integration to the
Linux CI jobs on the `namespace-runner-trial` branch.

When `runner_provider: namespace` is dispatched, the 8 Linux CI jobs
that install dependencies now:
1. Mount a Namespace Cache Volume via `nscloud-cache-action` covering
`~/.cache/yarn`, `.metamask`, `node_modules`, `.yarn/cache`, and
`.yarn/install-state.gz`
2. Skip `actions/setup-node` Yarn caching (set to empty string) to avoid
duplicate network-backed cache traffic
3. Skip `actions/cache` for `node_modules` in `component-view-tests` and
`merge-unit-and-component-view-tests` (Namespace cache already covers
it)

When `runner_provider: current` (the default on every existing trigger),
all ternaries collapse to their prior values and behavior is
byte-identical to the base branch.

**No job is renamed. No default is changed.** This is an additive,
opt-in change activated only via manual `workflow_dispatch` with
`runner_provider: namespace`.

## **Changelog**

CHANGELOG entry: null

## **Related issues**

Fixes: INFRA-3593 (parent epic INFRA-3511)
Refs: INFRA-3592 (Phase 0, PR MetaMask#29557)

## **Manual testing steps**

```gherkin
Feature: Namespace Cache Volumes on Linux CI

  Scenario: dispatch with namespace provider — cache volumes active
    Given the branch phase1-namespace-linux-cache
    When user runs `gh workflow run ci.yml --ref phase1-namespace-linux-cache -f runner_provider=namespace`
    Then all 8 Linux CI jobs with dependencies use nscloud-cache-action
    And actions/setup-node Yarn caching is disabled (no duplicate cache traffic)
    And all jobs pass across every matrix shard (unit-tests x10, component-view-tests x2, scripts x6)

  Scenario: dispatch with current provider — byte-identical to base
    Given the branch phase1-namespace-linux-cache
    When user runs `gh workflow run ci.yml --ref phase1-namespace-linux-cache -f runner_provider=current`
    Then nscloud-cache-action steps are skipped (if condition is false)
    And actions/setup-node uses cache: yarn as before
    And actions/cache for node_modules runs as before
    And all jobs pass on GitHub-hosted runners

  Scenario: implicit current via PR/push trigger
    Given a push or pull_request event (no workflow_dispatch)
    Then inputs.runner_provider is undefined/empty
    And all ternaries collapse to existing behavior
```

## **Screenshots/Recordings**

### **Before**

N/A

### **After**

N/A — CI infrastructure PR, no UI surface.

## **Pre-merge author checklist**

- [x] I've followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask Mobile
Coding
Standards](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/CODING_GUIDELINES.md).
- [x] I've completed the PR template to the best of my ability
- [x] I've included tests if applicable
- [x] I've documented my code using [JSDoc](https://jsdoc.app/) format
if applicable
- [x] I've applied the right labels on the PR (see [labeling
guidelines](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/LABELING_GUIDELINES.md)).
Not required for external contributors.

#### Performance checks (if applicable)

N/A — workflow YAML only, no app code.

## **Pre-merge reviewer checklist**

- [ ] I've manually tested the PR (e.g. pull and build branch, run the
app, test code being changed).
- [ ] I confirm that this PR addresses all acceptance criteria described
in the ticket it closes and includes the necessary testing evidence such
as recordings and or screenshots.

Made with [Cursor](https://cursor.com)

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Medium Risk**
> Touches many GitHub Actions workflows to optionally switch runner
labels and caching behavior, which could break CI execution or cause
cache-related flakiness when enabled. Default behavior remains unchanged
unless `runner_provider=namespace` is explicitly selected.
> 
> **Overview**
> Introduces a `runner_provider` input (with `workflow_dispatch` choices
where relevant) to route jobs between existing runners and new
`namespace-profile-*` runner labels across `ci.yml`, reusable build
workflows, and E2E smoke/regression workflows.
> 
> When `runner_provider=namespace`, Linux CI jobs that install
dependencies mount Namespace cache volumes via
`namespacelabs/nscloud-cache-action`, disable `actions/setup-node` Yarn
caching, and skip `actions/cache`-based `node_modules` restores in
coverage-merge/component-view jobs; Node memory limits are also reduced
on Namespace runners.
> 
> Updates `actionlint` configuration to allow the new Namespace runner
profile labels.
> 
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
3a52111. Bugbot is set up for automated
code reviews on this repo. Configure
[here](https://www.cursor.com/dashboard/bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

---------

Co-authored-by: Jose Luque <jose.luque@consensys.net>
Co-authored-by: José Manuel <6741785+jluque0101@users.noreply.github.com>
Co-authored-by: Cursor <cursoragent@cursor.com>

Author: 3 people

.github/workflows/ci.yml

@@ -94,10 +94,19 @@ jobs:
       - get_requirements
     steps:
       - uses: actions/checkout@v6
+      - name: Configure Namespace cache
+        if: ${{ inputs.runner_provider == 'namespace' }}
+        uses: namespacelabs/nscloud-cache-action@15799a6b54e5765f85b2aac25b3f0df43ed571c0 # v1
+        with:
+          path: |
+            ~/.cache/yarn
+            .metamask
+            node_modules
+            .yarn/cache
       - uses: actions/setup-node@v6
         with:
           node-version-file: '.nvmrc'
-          cache: yarn
+          cache: ${{ inputs.runner_provider != 'namespace' && 'yarn' || '' }}
       - name: Install Yarn dependencies with retry
         uses: nick-fields/retry@ce71cc2ab81d554ebbe88c79ab5975992d79ba08 #v3.0.2
         with:
@@ -130,10 +139,19 @@ jobs:
       - get_requirements
     steps:
       - uses: actions/checkout@v6
+      - name: Configure Namespace cache
+        if: ${{ inputs.runner_provider == 'namespace' }}
+        uses: namespacelabs/nscloud-cache-action@15799a6b54e5765f85b2aac25b3f0df43ed571c0 # v1
+        with:
+          path: |
+            ~/.cache/yarn
+            .metamask
+            node_modules
+            .yarn/cache
       - uses: actions/setup-node@v6
         with:
           node-version-file: '.nvmrc'
-          cache: yarn
+          cache: ${{ inputs.runner_provider != 'namespace' && 'yarn' || '' }}
       - name: Install Yarn dependencies with retry
         uses: nick-fields/retry@ce71cc2ab81d554ebbe88c79ab5975992d79ba08 #v3.0.2
         with:
@@ -170,10 +188,19 @@ jobs:
       - uses: actions/checkout@v6
         with:
           fetch-depth: 2
+      - name: Configure Namespace cache
+        if: ${{ inputs.runner_provider == 'namespace' }}
+        uses: namespacelabs/nscloud-cache-action@15799a6b54e5765f85b2aac25b3f0df43ed571c0 # v1
+        with:
+          path: |
+            ~/.cache/yarn
+            .metamask
+            node_modules
+            .yarn/cache
       - uses: actions/setup-node@v6
         with:
           node-version-file: '.nvmrc'
-          cache: yarn
+          cache: ${{ inputs.runner_provider != 'namespace' && 'yarn' || '' }}
       - name: Install Yarn dependencies with retry
         uses: nick-fields/retry@ce71cc2ab81d554ebbe88c79ab5975992d79ba08 #v3.0.2
         with:
@@ -205,10 +232,19 @@ jobs:
       statuses: write
     steps:
       - uses: actions/checkout@v6
+      - name: Configure Namespace cache
+        if: ${{ inputs.runner_provider == 'namespace' }}
+        uses: namespacelabs/nscloud-cache-action@15799a6b54e5765f85b2aac25b3f0df43ed571c0 # v1
+        with:
+          path: |
+            ~/.cache/yarn
+            .metamask
+            node_modules
+            .yarn/cache
       - uses: actions/setup-node@v6
         with:
           node-version-file: '.nvmrc'
-          cache: yarn
+          cache: ${{ inputs.runner_provider != 'namespace' && 'yarn' || '' }}
       - name: Install Yarn dependencies with retry
         uses: nick-fields/retry@ce71cc2ab81d554ebbe88c79ab5975992d79ba08 #v3.0.2
         with:
@@ -469,10 +505,19 @@ jobs:
         shard: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
     steps:
       - uses: actions/checkout@v6
+      - name: Configure Namespace cache
+        if: ${{ inputs.runner_provider == 'namespace' }}
+        uses: namespacelabs/nscloud-cache-action@15799a6b54e5765f85b2aac25b3f0df43ed571c0 # v1
+        with:
+          path: |
+            ~/.cache/yarn
+            .metamask
+            node_modules
+            .yarn/cache
       - uses: actions/setup-node@v6
         with:
           node-version-file: '.nvmrc'
-          cache: yarn
+          cache: ${{ inputs.runner_provider != 'namespace' && 'yarn' || '' }}
       - name: Install Yarn dependencies with retry
         uses: nick-fields/retry@ce71cc2ab81d554ebbe88c79ab5975992d79ba08 #v3.0.2
         with:
@@ -488,7 +533,7 @@ jobs:
       # in sync with the length of matrix.shard
       - run: yarn test:unit --shard=${{ matrix.shard }}/10 --forceExit --silent --coverageReporters=json --json --outputFile=tests/results/unit-test-results-${{ matrix.shard }}.json
         env:
-          NODE_OPTIONS: --max_old_space_size=20480
+          NODE_OPTIONS: ${{ inputs.runner_provider == 'namespace' && '--max_old_space_size=12288' || '--max_old_space_size=20480' }}
       - name: Rename coverage report and extract test count for this shard
         shell: bash
         run: |
@@ -520,7 +565,17 @@ jobs:
     if: ${{ !cancelled() && github.event_name != 'merge_group' }}
     steps:
       - uses: actions/checkout@v6
+      - name: Configure Namespace cache
+        if: ${{ inputs.runner_provider == 'namespace' }}
+        uses: namespacelabs/nscloud-cache-action@15799a6b54e5765f85b2aac25b3f0df43ed571c0 # v1
+        with:
+          path: |
+            ~/.cache/yarn
+            .metamask
+            node_modules
+            .yarn/cache
       - name: Restore node_modules cache
+        if: ${{ inputs.runner_provider != 'namespace' }}
         id: cache-node-modules
         uses: actions/cache@v4
         with:
@@ -531,9 +586,9 @@ jobs:
       - uses: actions/setup-node@v6
         with:
           node-version-file: '.nvmrc'
-          cache: yarn
+          cache: ${{ inputs.runner_provider != 'namespace' && 'yarn' || '' }}
       - name: Install Yarn dependencies with retry
-        if: steps.cache-node-modules.outputs.cache-hit != 'true'
+        if: ${{ inputs.runner_provider == 'namespace' || steps.cache-node-modules.outputs.cache-hit != 'true' }}
         uses: nick-fields/retry@ce71cc2ab81d554ebbe88c79ab5975992d79ba08 #v3.0.2
         with:
           timeout_minutes: 10
@@ -641,7 +696,17 @@ jobs:
         shard: [1, 2]
     steps:
       - uses: actions/checkout@v6
+      - name: Configure Namespace cache
+        if: ${{ inputs.runner_provider == 'namespace' }}
+        uses: namespacelabs/nscloud-cache-action@15799a6b54e5765f85b2aac25b3f0df43ed571c0 # v1
+        with:
+          path: |
+            ~/.cache/yarn
+            .metamask
+            node_modules
+            .yarn/cache
       - name: Restore node_modules cache
+        if: ${{ inputs.runner_provider != 'namespace' }}
         id: cache-node-modules
         uses: actions/cache@v4
         with:
@@ -652,9 +717,9 @@ jobs:
       - uses: actions/setup-node@v6
         with:
           node-version-file: '.nvmrc'
-          cache: yarn
+          cache: ${{ inputs.runner_provider != 'namespace' && 'yarn' || '' }}
       - name: Install Yarn dependencies with retry
-        if: steps.cache-node-modules.outputs.cache-hit != 'true'
+        if: ${{ inputs.runner_provider == 'namespace' || steps.cache-node-modules.outputs.cache-hit != 'true' }}
         uses: nick-fields/retry@ce71cc2ab81d554ebbe88c79ab5975992d79ba08 #v3.0.2
         with:
           timeout_minutes: 10
@@ -671,7 +736,7 @@ jobs:
             --json \
             --outputFile=tests/results/cv-test-results-${{ matrix.shard }}.json
         env:
-          NODE_OPTIONS: --max-old-space-size=20480
+          NODE_OPTIONS: ${{ inputs.runner_provider == 'namespace' && '--max-old-space-size=12288' || '--max-old-space-size=20480' }}
       - name: Rename coverage report and extract test count for this shard
         shell: bash
         run: |
@@ -860,6 +925,15 @@ jobs:
       - uses: actions/checkout@v6
         with:
           fetch-depth: 0 # SonarCloud needs a full checkout to perform necessary analysis
+      - name: Configure Namespace cache
+        if: ${{ inputs.runner_provider == 'namespace' }}
+        uses: namespacelabs/nscloud-cache-action@15799a6b54e5765f85b2aac25b3f0df43ed571c0 # v1
+        with:
+          path: |
+            ~/.cache/yarn
+            .metamask
+            node_modules
+            .yarn/cache
       - uses: actions/setup-node@v6
         with:
           node-version-file: '.nvmrc'