Auto-publish high-confidence YouTube-derived stalls

## Parent PRD

#1

## What to build

Turn on auto-publication for high-confidence YouTube-derived stalls once transcript-backed shadow ingestion, canonical matching, and freshness metadata are in place. This slice should let YouTube and Sheets act as equal stall sources while enforcing the minimum publication threshold and newer-source conflict policy from the PRD.

## Acceptance criteria

- [ ] YouTube-derived stalls publish only when transcript-backed parsing yields a high-confidence record with a name, country, and mappable place signal.
- [ ] Publication and merge behavior respect the newer-source policy and the bias toward false negatives.
- [ ] Tests cover end-to-end publication decisions and protect existing public stall browsing behavior.

## Blocked by

- Blocked by #8

## User stories addressed

Reference by number from the parent PRD:

- User story 1
- User story 16
- User story 18
- User story 20
- User story 21
- User story 22
- User story 25
- User story 26
- User story 27
- User story 28
- User story 30