* fix(core): harden audio FX and group identity
* fix(core): address audio group review feedback
* fix(core): align preview transport with grouped audio
* test(core): pin audio group gain ceiling
* fix(core): preserve solo bridge through stack
* fix(engine): harden grouped audio rendering
* docs(engine): explain grouped mix fallback invariant
* test(engine): allow grouped mixes to finish on Windows
* feat(lint): validate audio group membership and timing
* test(lint): pin audio group membership guards
* fix(studio): unify audio IDs and group state
* fix(studio): make audio-group edits transactional
* fix(studio): keep preview state synchronized
* fix(studio): align audio rows, automation lanes and headers
* fix(studio): stabilize timeline audio derivations
* refactor(studio): simplify group metadata memoization
* style(studio): keep timeline layout within size gate
* fix(studio): keep timeline preset apply off auditions
* fix(studio): harden carve and FX rack behavior
* fix(studio): repeat audio FX reveal requests
* fix(studio): reconnect property-panel audio controls
* fix(studio): unify property panel audio detection
* fix(studio): satisfy panel and deletion gates
* feat(studio,core)!: remove solo and the group meter
* docs(audio): keep removal rationale current
* refactor(core): retire studio solo bridge
* docs(audio): document grouped audio and its guardrails
* docs(audio): point handoff at replacement stack
