ci(board): discharge the bug-repro board to manual dispatch

The qa/** push trigger auto-ran the board from every qa branch, and the board
is structurally red on GitHub runners: its real-repo corpus tier hardcodes a
local path no runner can satisfy, so every auto-run failed on the skip gate
regardless of the code under test -- red that blocks nobody trains everyone
to ignore red. The board's primary venue is the local multi-leg CI, which can
hold the corpus; workflow_dispatch remains for cross-platform spot checks.

Scope: removes the push trigger only. The workflow was never a required check
(non-gating by its own declaration), so no gating change on any branch.

Signed-off-by: Martin Vogel <martin.vogel.tech@gmail.com>

.github/workflows/bug-repro.yml

@@ -15,12 +15,12 @@ on:
         type: choice
         options: ['all', 'linux', 'macos', 'windows']
         default: 'all'
-  # Iteration convenience: any push to a qa/** branch runs the board straight
-  # from that branch's own copy of this file (no main merge needed). Non-gating.
-  push:
-    # Exclude the dedicated lane branches so they only run their own workflow
-    # (fast-repro / soak / smoke), not the full board too.
-    branches: ['qa/**', '!qa/fast-**', '!qa/soak-**', '!qa/smoke-**']
+  # DISPATCH-ONLY by decision (2026-08-02): the board's primary venue is the
+  # LOCAL multi-leg CI (scripts/repro.sh on macOS/Linux/Windows), which can hold
+  # the real-repo corpus tier that GitHub runners never can -- the old qa/**
+  # push trigger auto-ran a board that was structurally red from those corpus
+  # skips, repainting red that blocked nobody. Manual dispatch remains for
+  # cross-platform spot checks (gh workflow run bug-repro.yml --ref <branch>).
 
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