ci(smoke-test): promote linux-arm64 from experimental to required gate

linux-arm64 has now had 5 consecutive green runs since being added
to the matrix in A-3 (matrix expansion):
  25947219129 (A-3 introduction)        → success
  25947614795 (cross-env)                → success
  25955832357 (test:unit dir path)       → success
  25956072211 (CRLF normalisation)       → success
  25956409080 (rollback dry-run docs)    → success

The promotion criterion documented in the workflow comment ("5
consecutive green runs without revert") is met. Concrete change:
  - matrix entry experimental: true → false
  - continue-on-error: ${{ matrix.experimental }} now resolves to
    false for this entry, meaning a red linux-arm64 build will fail
    the Smoke test summary job

Rationale: the linux-arm64 launcher rollout follows the Mac launcher
release window; tightening the safety net now (before any ARM-
specific code lands) gives us earlier warning of platform-
specific regressions.

windows-x64 remains experimental: it only had 1-2 consecutive greens
after recovering from a string of platform-specific blockers
yesterday (env-var-prefix syntax, node --test glob expansion, CRLF
in test scanner). Needs ~3 more clean runs before promotion. Comment
in the matrix entry documents the next-likely blocker (build:gui
cp -r command) so whoever promotes it next knows where to look.

Header comment in the workflow file also updated to reflect the new
gate status. No behavioural change for the existing required gates
(linux-x64, darwin-arm64).

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: SashaMIT

.github/workflows/smoke-test.yml

@@ -21,11 +21,11 @@ name: Smoke test (build + boot)
 #   - Any dependency / workspace install break (the v1.2.7.x lockfile drift class)
 #   - v1.2.7.11 osascript apostrophe regression (via test:unit step)
 #
-# Phase 5 (A-3, this revision): matrix expansion to ubuntu-24.04-arm +
-# windows-latest as experimental gates that surface platform-specific
-# regressions ahead of the Linux-ARM / Windows launcher rollout that
-# follows the Mac launcher. These DO NOT block release tagging until
-# proven stable; see continue-on-error on the matrix.
+# Phase 5 (A-3, A-3.1): matrix expansion to ubuntu-24.04-arm +
+# windows-latest. linux-arm64 promoted to required gate 2026-05-16
+# after 5 consecutive green runs since matrix introduction. windows-x64
+# remains experimental until it has the same green streak; see
+# continue-on-error on the matrix.
 #
 # Future phases (separate PRs against this workflow): heartbeat probe,
 # macOS permissions probe, pre-tag checklist, rollback runbook.
@@ -42,11 +42,11 @@ name: Smoke test (build + boot)
 #
 # Cost: $0. Public repo, standard runners. All four matrix entries
 # (ubuntu-latest, macos-latest, ubuntu-24.04-arm, windows-latest) are
-# free for public repos. Observed timings on this branch:
+# free for public repos. Observed timings:
 #   - linux-x64       ~4 min cold cache
+#   - linux-arm64     ~5 min cold cache (required gate as of 2026-05-16)
 #   - darwin-arm64    ~7 min cold cache
-#   - linux-arm64     not yet measured (first run with this matrix)
-#   - windows-x64     not yet measured (first run with this matrix)
+#   - windows-x64     ~8 min cold cache (still experimental — see matrix)
 # Total wall-clock is bounded by the slowest entry because matrix
 # entries run in parallel.
 
@@ -93,8 +93,7 @@ jobs:
       matrix:
         include:
           # ── Required gates ────────────────────────────────────────────
-          # These two MUST be green before the launcher is tagged. They
-          # cover the platforms we ship to users next Wed/Thu. A red
+          # These MUST be green before the launcher is tagged. A red
           # entry here fails the Smoke test summary job and prevents
           # release tagging once branch protection is enabled on main.
           - os: ubuntu-latest
@@ -103,31 +102,29 @@ jobs:
           - os: macos-latest
             label: darwin-arm64
             experimental: false
+          # linux-arm64 promoted 2026-05-16 after 5 consecutive green
+          # runs since A-3 matrix expansion (runs 25947219129,
+          # 25947614795, 25955832357, 25956072211, 25956409080).
+          # The Linux ARM build chain has proven identical to x86_64
+          # under our apt-get + canvas system-libs setup; promoting it
+          # tightens the safety net for the post-Mac ARM rollout.
+          - os: ubuntu-24.04-arm
+            label: linux-arm64
+            experimental: false
 
-          # ── Experimental gates (A-3 matrix expansion) ────────────────
-          # These two run on every push but are NOT release blockers.
-          # They surface platform-specific regressions ahead of the
-          # Linux-ARM / Windows launcher rollout after the Mac release
-          # ships. continue-on-error: true (set below) means a red entry
-          # here lands as a yellow advisory on the dashboard rather than
-          # a red workflow failure.
+          # ── Experimental gates ───────────────────────────────────────
+          # Run on every push but NOT release blockers. continue-on-error
+          # is wired below so a red entry here is a yellow advisory.
           #
-          # Expected initial state:
-          #   - ubuntu-24.04-arm: likely green. Build chain is Unix and
-          #     apt-get canvas libs work the same on arm64. If red,
-          #     diagnose and fix incrementally.
-          #   - windows-latest: likely red on typecheck because canvas@2
-          #     building from source on Windows needs MSVC + GYP +
-          #     non-trivial setup; we explicitly do NOT install canvas
-          #     system libs on Windows in this phase. The Phase 2 canvas
-          #     migration to @napi-rs/canvas removes this entire concern.
+          # Promotion criterion: 5 consecutive green runs without revert.
           #
-          # Promotion path: once an experimental entry has been green for
-          # 5 consecutive pushes, flip its `experimental: true` to false
-          # to make it a required gate.
-          - os: ubuntu-24.04-arm
-            label: linux-arm64
-            experimental: true
+          # windows-x64 status (2026-05-16): green for the first time on
+          # run 25956072211 after fixing (a) env-var-prefix syntax via
+          # cross-env, (b) node --test glob expansion, (c) CRLF in test
+          # source scanner. Only 1-2 consecutive greens so far; needs
+          # ~3 more clean runs before promotion. Next potential blocker
+          # (when investigated): the build:gui cp -r command may need
+          # cross-platform replacement in Phase 2.
           - os: windows-latest
             label: windows-x64
             experimental: true