ChannelTalk Clone E/F Integration Checkpoint

E/F integrated into local clone. Baseline commit: 09947ea (Add mapping inspector and visual fidelity pass). Previous baseline: 91899d8.

Verification: npm run lint pass, npm run build pass, npm run db:seed pass with 24 guide records, npm run db:import:mappings pass with 24 guide records. Runtime smoke on temporary next start :3052 passed for /api/mappings/guides, guide detail, and /mappings page shell.

Read: /home/tlswk/projects/re-center/channel-talk/pm/INTEGRATION_CHECKPOINT_20260706_EF.md

Next recommended: stabilization UI smoke across Inbox, ALF, mappings; final desktop/mobile screenshots; then Session G Mattermost POC if still desired.