Make speaker profile merges atomic on current main

[r3dbars]

Summary

Current-main replacement for #1546. Speaker naming finalization now keeps transcript edits and planned speaker-database mutations inside the existing serialized transcript update boundary, with one database mutation batch and transcript rollback if persistence fails. It preserves newer main-only transcript path resolution and speaker-finalization retry behavior, and does not reintroduce the deleted fast-test manifest.

Proof plan

• current-main exact-head review and merge simulation
• git diff --check
• bash build-deps.sh --force
• bash build.sh --no-open
• bash run-tests.sh
• bash run-integration-smoke.sh
• swift test
• speaker merge focused tests
• manual Settings speaker merge remains UNKNOWN

Disposition

Replaces #1546 after merge; old branch conflicts with current speaker finalization work.

lanes used: Codex=repair and final verification; Claude=advisory risk review; Local=unavailable; Windows=skipped because macOS/SQLite-specific.

[r3dbars]

Superseded by current-main replacement #1567, which carries the same speaker repair rebased to the live queue.

[r3dbars]

Superseded by current-main replacement PR #1567 after live main advanced through #1565. The repaired speaker merge lineage remains open there, with the persistence-failure compile/recovery fixes.