dashboard: scrollController test warns on unexpected scroll-to-top fails deterministically on clean tree (blocks CI dashboard-suite addition) #974

Symptom

The dashboard vitest suite has one deterministic failure on a clean main checkout, independent of any in-flight PR:

FAIL  packages/dashboard/__tests__/scrollController.test.ts
  ScrollController > onScroll handler
    × warns on unexpected scroll-to-top but does not auto-correct (Issue #630)
      AssertionError: expected "warn" to be called at least once
      Number of calls: 0

The rest of the dashboard suite passes (316 / 318 with 1 skipped — this is the sole failure). Verified on two separate builder worktrees (pir-961, pir-875) running against clean main HEADs minutes apart — failure is reproducible, not flaky.

Distinct from #630

#630 is closed and was about the runtime bug — xterm parsing errors + WebGL context loss causing terminals to scroll to the top unexpectedly. That runtime bug's mitigation ships in ScrollController.handleScroll + the term.write callback and the user-facing terminal behavior works (no terminals scrolling to top on contact).

This issue is about the test added alongside that mitigation — the assertion expects warnSpy to have been called at least once is no longer satisfied. So either:

1. The mitigation's warn path has been removed or refactored without updating the test
2. The test fixture no longer reproduces the scroll-to-top trigger that's supposed to fire the warning
3. The warnSpy is hooked to the wrong target after some refactor

The user-facing behavior #630 was filed to fix appears unaffected; this is a test-suite hygiene problem, not a regression of the original bug.

Why it matters now

#967 tracks adding the vscode + dashboard vitest suites to CI (today neither runs). Promoting the dashboard suite to a required check requires this test to be green on clean main, OR the test to be deleted / quarantined / its assertion corrected. #967 explicitly cites this failure as the blocker for the dashboard side.

Suggested investigation order

1. Read the failing test: packages/dashboard/__tests__/scrollController.test.ts — the onScroll handler > warns on unexpected scroll-to-top describe block. Check what trigger the test stages and what warnSpy is hooked to.
2. Read ScrollController in the dashboard source — verify whether the warn it expects to be called still exists, and whether the trigger conditions still apply.
3. Run git log -p on both files since the last green run to see what changed.
4. Decide on shape: if the warn path is gone by design, the test should be updated or deleted; if the warn path regressed silently, fix the code; if the test fixture is stale, fix the fixture.

Acceptance

• The test warns on unexpected scroll-to-top but does not auto-correct (Issue #630) either passes on a clean main checkout, or is replaced / deleted with a clear-headed reason recorded
• Whatever the resolution shape, the user-facing scroll-to-top mitigation #630 shipped is preserved (no regression to the runtime behavior)
• pnpm --filter @cluesmith/codev-dashboard test exits 0 on clean main (full suite green, no skipped tests added beyond the existing 1)
• No new flakiness introduced (test failure was deterministic; fix should preserve determinism in either direction)

Out of scope

• Adding the dashboard suite to CI — that's #967's job. This issue is the prerequisite that unblocks it.
• Any change to the runtime ScrollController.handleScroll or term.write callback unless the test failure root-causes there (in which case it's not really out of scope)

Why BUGFIX

Isolated test or small mitigation-code adjustment — likely <50 LOC net diff. No design surface (the answer is "make the assertion match reality" or "make the code match the assertion"; one of them is wrong, the investigation reveals which). No new module or pattern.

Related

• #630 — original runtime bug (closed); this test was added to pin its mitigation
• #967 — CI-gap follow-up that's blocked on this test being green