CI: extension frames check intermittently times out at "palette access inside a real modal shell"

[Juliusolsson05]

scripts/check-extension-frames.mjs (run by src/main/extensions/electron.system.test.ts in the quality gate) intermittently fails on the macOS runner:

Error: palette access inside a real modal shell timed out: {"text":"Extension input fixture", ... "shell=modal" ...}
    at waitFor (main.cjs)
Error occurred in handler for 'extensions:runtime-host': Error: This extension does not declare activation for onCommand:managed.snapshot.

Seen twice:

• main on 2026-09-23, run 35806171133 (job 107007411145).
• PR feat(updates): opt-in Preview update channel #1169 on 2026-09-24, run 36073908733 (job 107880940546). That PR does not touch extensions or the palette.

Per the repo's rule that a waitFor timeout is not flakiness, this needs a root cause: most likely an ordering race between the modal shell mounting and the palette-access probe. Don't widen the timeout.

🤖 Generated with Claude Code

[Juliusolsson05]

Another occurrence on PR #1105 (head 0ccc33d8): https://github.com/Juliusolsson05/agent-code/actions/runs/36076581349. That PR does not touch src/main/extensions/ or anything the harness imports (renderer-only, plus one new kill-caller string), so it is independent of the change under test.

[Juliusolsson05]

Two more occurrences, same signature (palette access inside a real modal shell timed out → Extension Electron checks failed (1)):

• main at 00ef622 (merge of fix(terminals): keep a terminal's last-used time across restarts #1179): run 36083212778
• PR feat(composer): lock the composer and show the prompt as Sending in the feed #1183 at daefde7: run 36084020892. That PR touches only the composer, feed and JSONL flush, not extensions. It was the only failure among 6508 tests.

🤖 Generated with Claude Code

[Juliusolsson05]

Fixed by #1300 (merged 1d25b0ed). This is the same failure as #1261: the palette chord was pressed before Electron's focusedFrame reached the extension frame. The harness now waits for the focused frame, matched by processId + routingId, for both the pane step and the modal step, without widening any budget. Reopen if palette access inside a real modal shell timed out recurs on a head that contains 1d25b0ed. The real-app gap (a chord does nothing until the modal iframe has focus) is #1307.