docs(testing): document CV flakiness and high-leverage assert patterns

[racitores]

Description

Expands component-view guidance with patterns learned from Mobile CV work:

1. Stale press targets (Mobile #34241) — do not hold an element across awaits when the UI re-renders on a timer; re-query immediately before fireEvent.press. Prefer default { name: Routes.X } route probes.
2. Migration assert parity (MMQA-2104 / Mobile #34197) — unit→CV must not weaken deleted expects (tabId, filterId, formatted dates, full analytics). Mandatory gap-check in unit-cv-overlap.
3. Filter both-sides — Golden Rule 10 already required this; add an explicit antipattern: analytics/refetch alone is not enough — seed distinct before/after rows.
4. Loading / skeleton honesty — pending-phase tests must match production UX (skeleton / not-yet-visible), not optimistic titles the screen does not show while loading.
5. RefreshControl + flag overrides — call refreshControl.props.onRefresh inside act; drive flag-gated sheets via Redux / remote-flag overrides.

Files updated (testing/mobile-testing)

• references/component-view.md — Golden Rules 10–12
• references/component-view/writing-tests.md — high-leverage interaction pitfalls
• references/component-view/navigation-mocking.md — analytics-only filter antipattern
• references/component-view/reference.md — self-review 5/11–13, diagnosing failures, assertion patterns, What NOT to Do
• references/placement/unit-cv-overlap.md — mandatory assert-parity gap check before DELETE
• CHANGELOG.md

Type of Change

• Skill improvement/update
• New skill
• Bug fix
• Documentation update
• Other (please describe):

Checklist

• I have read the CONTRIBUTING.md guidelines
• My skill follows the SKILL_TEMPLATE.md format
• I have tested this skill with an AI agent
• My skill does not contain any secrets, private keys, or sensitive data
• I have added appropriate documentation
• My changes don't break existing skills

Testing

Reviewed guidance against Mobile CV fixes in #34241 and the MMQA-2104 Predict unit↔CV pass (#34197). No installer/CLI behavior change.

Additional Context

Highest-leverage items first (parity, filter both-sides example, loading honesty, RefreshControl/flags), on top of the existing stale-press / route-probe docs.

After merge, Mobile consumers pick this up on next metamask-skills sync --include testing/mobile-testing. Companion in-repo doc sync for docs/testing/component-view-tests.md can follow separately if desired.