ci: allow manual E2E runs via workflow_dispatch

Add a workflow_dispatch trigger with platform and tier inputs so the E2E jobs on
the self-hosted GPU runners can be run on demand against any ref, without a push
or the full pipeline. A manual dispatch skips build-and-test for a fast loop;
nothing on the default branch depends on that job, so skipping it is safe here.

The trigger must exist on the default branch for the workflow to be dispatchable
at all; the E2E jobs that consume these inputs live on their own branch and are
run by dispatching against that ref.

Signed-off-by: fredespi <fredrik.espinoza@gmail.com>

Author: fredespi

.github/workflows/ci.yml

@@ -10,6 +10,24 @@ on:
   merge_group:
     branches: [main]
     types: [checks_requested]
+  # Manual trigger for on-demand E2E runs on the self-hosted GPU runners, without
+  # waiting on a push/PR or the full gate. Dispatch against any ref
+  # (`gh workflow run ci.yml --ref <branch> -f platform=... -f tier=...`) — GitHub
+  # runs THAT ref's copy of this file, so the E2E jobs it selects live on the ref.
+  # A dispatch skips build-and-test (see its `if:`) for a fast loop. This trigger
+  # must exist on the default branch for the workflow to be dispatchable at all.
+  workflow_dispatch:
+    inputs:
+      platform:
+        description: Which GPU runner(s) to target
+        type: choice
+        default: all
+        options: [all, app-dev-gpu, strix-ubuntu, strix-windows]
+      tier:
+        description: Which scenario tier(s) to run
+        type: choice
+        default: both
+        options: [both, expect-pass, known-bugs]
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
@@ -96,6 +114,9 @@ jobs:
     runs-on: ubuntu-latest
     # Don't spend per-OS build/test cycles unless the cheap lint gate is green.
     needs: [changes, clippy, prek]
+    # A manual E2E dispatch skips this heavy job for a fast loop; the E2E jobs
+    # tolerate a skipped build-and-test in their own `if:` guards.
+    if: github.event_name != 'workflow_dispatch'
     steps:
       - uses: actions/checkout@v6