feat: browse handoff — headless-to-headed browser switching (v0.7.4) (#201)

* feat: browse handoff — headless-to-headed browser switching

Add `handoff` and `resume` commands that let users take over a visible
Chrome when the headless browser gets stuck (CAPTCHAs, auth walls, MFA).

Architecture: launch-first-close-second for safe rollback. State transfer
via extracted saveState()/restoreState() helpers (DRY with recreateContext).
Auto-handoff hint after 3 consecutive command failures.

* test: handoff unit + integration tests (15 tests)

Covers saveState/restoreState, failure tracking, edge cases (already
headed, resume without handoff), and full integration flow with cookie
and tab preservation across headless-to-headed switch.

* docs: handoff section in browse template + TODOS update

Add User Handoff section to browse/SKILL.md.tmpl with usage examples.
Update State Persistence TODO noting saveState/restoreState reusability.

* chore: bump version and changelog (v0.7.4)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

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Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>