test(desktop): cover composer mention catalog context guard

[Totoro-qaq]

Summary

Fixes #4892

Add three regression tests for ComposerMentionsProvider using the existing node:test + linkedom setup:

• Observe the first committed context value after switching sessions, before passive effects can hide stale Skills or an unavailable verdict.
• Cover switches from both populated and empty catalogs.
• Keep settled Skills visible during a same-context refresh until its response resolves.

Production code, dependencies, compiler configuration, and test locations are unchanged.

Verification

• npm --workspace @maka/desktop run build:main — passed.
• New suite: node --test --test-concurrency=4 dist/main/__tests__/composer-mentions.test.js from apps/desktop — 3 passed; also passed in 20 consecutive fresh processes.
• Existing agent-graph-panel and composer-directories suites — 23 passed.
• Mutation checks, each rebuilt from source:
  • Invert the context comparison — all 3 tests fail.
  • Remove the render guard — both session-switch tests fail.
  • Clear Skills during same-context refresh — the refresh test fails.
  • Restore production code and rebuild — all 3 tests pass.
• npm run lint, npm run format:check, npm run build, and npm run typecheck — passed.
• npx knip --workspace apps/desktop and npx knip --workspace packages/ui — passed.
• Desktop architecture checks — passed, including 101 checker tests.

Not run: full-repository npm test, Storybook browser smoke, or Electron GUI E2E.

AI use

• No generative tool made a substantive contribution
• Generative tooling made a substantive contribution

Tool(s) and scope:

• OpenAI Codex: test implementation and local verification.
• DeepSeek Harness (deepseek-v4-pro, reasoning effort max): independent read-only review and focused test execution.

Checklist

• Tests cover the change and fail without it
• Lint, format, typecheck and the affected suites pass locally

Does this PR entail a change in behavior?

• Yes — described under Summary above
• No

[Totoro-qaq]

@Astro-Han CI is currently blocked at check:e2e-budget:

session-workbar.spec.ts: budget records 5 test(s), the file has 6

The same mismatch is present on current main. This PR only adds a node:test file and does not change the Electron E2E tier or its budget.

Could you take a look at the budget mismatch? I've kept that unrelated change out of this PR.

TYSM！

Failed check

[hqhq1025]

Reviewed exact head c926fb260aee2914013965a239688618489df758. I found no P0-P3 issues in this test-only change.

The new apps/desktop/src/main/__tests__/composer-mentions.test.ts exercises the real ComposerMentionsProvider and reads the exposed catalog from a layout effect before the provider passive effect runs. It therefore pins the production timing contract: switching sessions immediately hides both populated and empty stale catalogs, while a same-context refresh retains settled skills. Independent mutation probes confirmed the tests fail if the context-key guard is inverted or if same-context refreshes clear the catalog.

Validation passed on the exact branch: clean install, build, Desktop typecheck, focused tests (26/26), full Desktop tests (2230/2230), renderer architecture (101/101), Biome/format, ASF headers, diff check, and the branch-local E2E budget. A clean synthetic merge with current main also built and passed focused tests (26/26), full Desktop tests (2289/2289), and architecture checks.

The required hosted test check is still red because the current merge tree contains an unrelated E2E budget mismatch in session-workbar.spec.ts (6 tests versus a budget of 5). The synthetic merge also exposes unrelated current-main Storybook type errors around WorkbarLayoutState.rightCollapsed. Neither path is touched by this PR, so I am not filing a PR finding for them, but the required gate is not green and this is not a merge approval.

Automated review notice: This comment was posted by an automated review agent operated by hqhq1025. It is not an independent human review and does not replace one.

[Totoro-qaq]

@Astro-Han Thanks for fixing the main-branch blockers in #4895! I've rebased onto main, and CI now passes at da01731.

The patch is unchanged: one test file covering #4892, with no production changes. Could you take a look when you have a chance?

tysm!

[Astro-Han]

Reviewed at da01731 against main (90014db94), +195/−0, one test file, CI green.

This is the test #4892 asked for, in the tier it asked for: ComposerMentionsProvider mounted through the existing node:test + linkedom path under src/main/__tests__, observing the first committed context after a Session switch before passive effects can hide stale Skills, from both populated and empty catalogs, plus the same-context refresh keeping settled Skills visible. The mutation checks in the body (inverted comparison, removed guard, cleared Skills on refresh) are the three regressions the guard exists to catch, and each is caught by at least one test. No production code touched.

Thanks for the report on the budget breakage too; #4895 fixed it on main.

AI-assisted review: drafted with Maka; I read the three tests against composer-mentions.tsx myself.