test(ELITEA-1739): search skills by name (skills module, first case)

[bermudas]

Summary

• Implements ELITEA-1739 ("search skills by name") as the skills module's first automated spec (tests/skills.spec.ts), per the re-verified AFS at test-specs/skills/l3_search-skills-by-name_ELITEA-1739.md.
• Adds two new page objects: tests/pages/skillForm.page.ts (create-form) and tests/pages/skillsList.page.ts (list/search) — greenfield module, no prior skills test surface existed.
• Key correctness detail carried over from the AFS's own re-verification: the main Skills list only filters after Enter is pressed post-fill() — fill() alone only opens a typeahead tooltip. Both phases are asserted separately (step 7 pre-Enter, step 7b post-Enter).
• Idempotent setup: ensureSkillsExist() checks for each of the 3 slug-valid skill names (formatter/code-reviewer/content-writer) before creating it, since the account may already carry them from an earlier analyst pass.
• Bundles the analyst's AFS file (test-specs/skills/l3_search-skills-by-name_ELITEA-1739.md) into this PR, since it was left uncommitted on disk per the analyst's own dispatch instruction.

Implementer-side fixes found during Phase 4/5 (infrastructure, not product defects)

• A first-run onboarding tour ("Jump in now!") and the recurring release-notes banner (GH#42) can both intercept the sidebar "Skills" nav click in a freshly-created browser.newContext({ storageState }) — the worker-scoped fixture's own dismissal (done in the login context) doesn't reliably carry over. Fixed with gotoSkillsListViaSidebar() (dismiss-then-click, with one retry if diverted to /app/onboarding).
• ensureSkillsExist() originally raced a bare .count() immediately after page.goto(), misdetecting an existing "formatter" skill as missing and creating a live duplicate (caught, and the duplicate manually deleted via the confirmed Skills delete-confirmation dialog, before re-running). Fixed by waiting for the authoritative GET .../skills/prompt_lib/... list response before checking.

Flagged for Tal (not actioned in this PR)

• trackConsoleErrors() is now duplicated in a 6th spec file, past .agents/testing.md's own "do not let a 6th module land before this happens" note on the deferred shared-fixture extraction (tests/fixtures/auth.ts + console-tracking helper). Framework-architecture decision, left for a dedicated framework-scale PR per Hard Rule (implementer executes plans, doesn't invent them).

Test plan

• npx playwright test --grep "ELITEA-1739" — green 3/3 consecutive local runs, no flake.
• Verified idempotency: account left with exactly 3 skills (no duplicates) after all runs.
• No CI variant yet (.agents/testing.md: "no CI yet ... 'CI' and 'local' are the same command").

Refs #127