Split CI between self-hosted and GitHub runners

Run the Rust build/test matrix, linting, docs, and benchmarks on the
self-hosted runner, but keep jobs the runner cannot serve on GitHub's
ubuntu-latest:

- Docker-based integration tests (cln, eclair, lnd, python, kotlin)
  and the Postgres/VSS service-container jobs, since the self-hosted
  runner has no Docker installed.
- Third-party node-action jobs (semver checks, security audit, nightly
  rustfmt), since the runner is too old to load actions that require
  the node24 runtime.

For the jobs that stay self-hosted, adapt to the runner environment:

- Pin actions/checkout to v4 and actions/cache to v4; their newer
  releases run on node24, which the self-hosted runner does not
  support.
- Install the Rust toolchain in its own step so rustup and cargo land
  on PATH for the steps that follow; invoking them in the same step as
  the rustup install fails because PATH is not refreshed mid-step.

Assisted by Claude Code.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: benthecarman

.github/workflows/benchmarks.yml

@@ -9,25 +9,26 @@ concurrency:
 jobs:
   benchmark:
     timeout-minutes: 60
-    runs-on: ubuntu-latest
+    runs-on: self-hosted
     env:
       TOOLCHAIN: stable
     steps:
       - name: Checkout source code
-        uses: actions/checkout@v6
+        uses: actions/checkout@v4
       - name: Install Rust toolchain
         run: |
           curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --profile=minimal --default-toolchain stable
-          rustup override set stable
+      - name: Set Rust override
+        run: rustup override set stable
       - name: Enable caching for bitcoind
         id: cache-bitcoind
-        uses: actions/cache@v5
+        uses: actions/cache@v4
         with:
           path: bin/bitcoind-${{ runner.os }}-${{ runner.arch }}
           key: bitcoind-29.0-${{ runner.os }}-${{ runner.arch }}
       - name: Enable caching for electrs
         id: cache-electrs
-        uses: actions/cache@v5
+        uses: actions/cache@v4
         with:
           path: bin/electrs-${{ runner.os }}-${{ runner.arch }}
           key: electrs-${{ runner.os }}-${{ runner.arch }}

.github/workflows/cron-weekly-rustfmt.yml

@@ -12,7 +12,7 @@ jobs:
   format:
     name: Nightly rustfmt
     timeout-minutes: 60
-    runs-on: ubuntu-24.04
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v6
       - uses: dtolnay/rust-toolchain@nightly

.github/workflows/hrn-integration.yml

@@ -9,7 +9,7 @@ concurrency:
 jobs:
   build-and-test:
     timeout-minutes: 60
-    runs-on: ubuntu-latest
+    runs-on: self-hosted
 
     steps:
       - name: Checkout source code

.github/workflows/rust.yml

@@ -12,7 +12,7 @@ jobs:
     strategy:
       matrix:
         platform: [
-          ubuntu-latest,
+          self-hosted,
           macos-latest,
           windows-latest,
           ]
@@ -25,7 +25,7 @@ jobs:
           - toolchain: stable
             check-fmt: true
             build-uniffi: true
-            platform: ubuntu-latest
+            platform: self-hosted
           - toolchain: stable
             platform: macos-latest
           - toolchain: stable
@@ -35,7 +35,7 @@ jobs:
     runs-on: ${{ matrix.platform }}
     steps:
       - name: Checkout source code
-        uses: actions/checkout@v6
+        uses: actions/checkout@v4
       - name: Install Rust ${{ matrix.toolchain }} toolchain
         run: |
           curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --profile=minimal --default-toolchain ${{ matrix.toolchain }}
@@ -51,13 +51,13 @@ jobs:
         run: echo "RUSTFLAGS=-D warnings" >> "$GITHUB_ENV"
       - name: Enable caching for bitcoind
         id: cache-bitcoind
-        uses: actions/cache@v5
+        uses: actions/cache@v4
         with:
           path: bin/bitcoind-${{ runner.os }}-${{ runner.arch }}
           key: bitcoind-29.0-${{ runner.os }}-${{ runner.arch }}
       - name: Enable caching for electrs
         id: cache-electrs
-        uses: actions/cache@v5
+        uses: actions/cache@v4
         with:
           path: bin/electrs-${{ runner.os }}-${{ runner.arch }}
           key: electrs-${{ runner.os }}-${{ runner.arch }}
@@ -94,14 +94,15 @@ jobs:
   linting:
     name: Linting
     timeout-minutes: 60
-    runs-on: ubuntu-latest
+    runs-on: self-hosted
     steps:
       - name: Checkout source code
-        uses: actions/checkout@v6
-      - name: Install Rust and clippy
+        uses: actions/checkout@v4
+      - name: Install Rust stable toolchain
         run: |
           curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --profile=minimal --default-toolchain stable
-          rustup component add clippy
+      - name: Add clippy component
+        run: rustup component add clippy
       - name: Ban `unwrap` in library code
         run: |
           cargo clippy --lib --verbose --color always -- -A warnings -D clippy::unwrap_used -A clippy::tabs_in_doc_comments
@@ -110,11 +111,11 @@ jobs:
   doc:
     name: Documentation
     timeout-minutes: 60
-    runs-on: ubuntu-latest
+    runs-on: self-hosted
     env:
       RUSTDOCFLAGS: -Dwarnings
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@nightly
       - uses: dtolnay/install@cargo-docs-rs
       - run: cargo docs-rs