A child who opened their Quest Log could only get back to the Party
board by waiting out the 40 s idle return. The header now carries a
72px "The Party" button (left chevron, left of the crest) that calls
the existing _returnToBoard() path the idle return uses. The idle
return, crest-tap navigation and 1c auto-return are unchanged.
Documented in PANEL-SPEC §3; jsdom test taps it and asserts navigation
to the strategy-computed board_path; bundle rebuilt.
Task: 987d2d0f-a5d1-4bb5-a1f3-80fd6adbf5e9
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>