Nightly 20260927

Nightly build of Voyage at 3c837b5f8a.

Changes since nightly 20260926:

• 3c837b5f8a Clarify validation and commit message rules
• 7db09536d2 Match profile personalization backgrounds and dividers
• d8e03cd114 Prevent timeline shifts when opening read-only rooms
• 3714a49ff1 Resolve lint findings and preserve API 14 support
• 6ece2fed52 Require tests and lint before committing
• e0afc2562a Exclude local echoes from thread reply counts
• ee40e48f77 Keep unread markers visible until their fade completes
• a90e46a36f Smooth composer keyboard transitions and preserve resume state
• 30645682ed Match downloaded audio backgrounds to MSC4549 cover art
• 142f025a78 Fix composer microphone layering and attachment transitions
• e2a0dd521a Preserve search mention pills when applying autocomplete
• 0374eb28ad Open MXC links as authenticated media downloads