P2: Participant-synced lower thirds and overlay automation

[iamfatness]

Problem

Lower thirds/overlays should follow participant assignments and active speaker changes, but overlays currently do not reliably affect OBS output.

Outcomes

• Lower third templates generate from live participant data.
• Manual name/title overrides persist per participant or per show profile.
• Overlay visibility and timing are controlled from Sidecar and reflected in OBS.

Acceptance criteria

• Assigned participant source displays matching name tag/lower third in OBS.
• Active speaker changes can update lower third state without stale names.
• Manual override wins over Zoom display name until cleared.

[iamfatness]

Hardened participant-synced lower-third override behavior in 0ff544c.

• Manual lower-third names/subtitles are now trimmed before overlay generation.
• Blank enabled manual name suppresses the auto-generated lower third, preserving the existing explicit-hide behavior.
• Expanded CoreVideoSidecarLowerThirds coverage for generated names, speaking subtitle, manual override, clear override, and showNameTag=false.

Verification run locally:

• cmake --build build-vs-release --config Release --target CoreVideoSidecarLowerThirdTest --parallel
• ctest --test-dir build-vs-release -C Release --output-on-failure -R CoreVideoSidecarLowerThirds
• ctest --test-dir build-vs-release -C Release --output-on-failure
• git diff --check

[iamfatness]

Progress on participant-synced lower thirds:

• Auto lower thirds now treat only participant ID 0 as empty/unassigned.
• Reserved Sidecar placeholder participants can now render generated lower thirds, so no-meeting look/template testing exercises the same path as live participants.
• Added a regression test for placeholder lower-third generation.

Validation:

• cmake --build build-vs-release --config Release --target CoreVideoSidecarLowerThirdTest --parallel
• ctest --test-dir build-vs-release -C Release --output-on-failure passed 8/8

Committed in 4afae9d.

[iamfatness]

Added live lower-third OBS sync in ca6cd9e.

What changed:

• Sidecar now generates participant-synced lower thirds through a shared helper for preview and program looks.
• Live participant updates now diff generated lower thirds and debounce an OBS program render when the on-air labels change.
• MEBus has a narrow replaceProgramLook() path for metadata/overlay updates without a transition or extra TAKE.

Why it matters:

• Name/speaking/screen-share lower-third changes no longer require another manual operator action before OBS can receive the updated overlay state.

Validation:

• cmake --build build-vs-release --config Release --target CoreVideoSidecar --parallel
• ctest --test-dir build-vs-release -C Release --output-on-failure (8/8 passed)
• git diff --check