chore(dogfood): Verify breaking finding via users.id PK drop

[mhiro2]

Summary

• Live verification PR for the mhiro2/relune/action review path: introduces a deliberately breaking change to dogfood/schema.sql so that the dogfood-review workflow surfaces a blocking finding on this PR's sticky comment.
• Not intended for merge — kept open for inspection of the rendered Markdown report. Once the comment is verified, the PR can be closed without merging.

Changes

• d544ced : chore(dogfood): drop users.id primary key to verify breaking finding
  • Replace id BIGINT PRIMARY KEY with id BIGINT NOT NULL on the users table while leaving posts.author_id and comments.author_id foreign keys pointing at users (id).
  • The diff produces a single risk/drop-pk-or-unique (breaking) finding because the rule fires when a primary key is dropped while existing foreign keys still reference the table.

[github-actions]

Caution

🛑 Blocking findings detected. Resolve them before merging.

Schema review

1 breaking · 0 caution · 0 warning · 0 info

Breaking

• risk/drop-pk-or-unique — users.id
  Primary key on users (id) is being dropped while FK posts_author_id_fkey on posts still references it. Migration will fail.
  mitigation: Drop or repoint the referencing FKs in the same migration.

[github-actions]

Code Metrics Report

	main (87c2b43)	#109 (f808c21)	+/-
Coverage	94.6%	94.6%	0.0%
Test Execution Time	1m28s	1m32s	+4s

Details

  |                     | main (87c2b43) | #109 (f808c21) | +/-  |
  |---------------------|----------------|----------------|------|
  | Coverage            |          94.6% |          94.6% | 0.0% |
  |   Files             |             81 |             81 |    0 |
  |   Lines             |          36827 |          36827 |    0 |
  |   Covered           |          34864 |          34864 |    0 |
- | Test Execution Time |          1m28s |          1m32s |  +4s |

---

Reported by octocov

[mhiro2]

Verified end-to-end behavior of the review GitHub Action via the dogfood
workflow on this PR — closing without merge as planned.

Confirmed on the rebased run (after #110 landed):

• The dogfood-review workflow runs on pull_request and posts a sticky
  comment keyed on <!-- relune-dogfood-review -->.
• A risk/drop-pk-or-unique breaking finding (PK drop with referencing
  FKs) is detected and rendered via format_review_markdown inside the
  comment body.
• The new [!CAUTION] alert envelope (🛑 leading emoji, "Resolve them
  before merging." call-to-action) renders as expected.
• The Fail when blocking step exits 1 so the workflow run reports
  failure once the comment is posted.
• The earlier [!TIP] (no findings) state was confirmed on chore(action): Polish review sticky comment with alerts and emoji #110 itself,
  so all three lifecycle paths now have live coverage.

Phase 2 completion criteria are now fully satisfied.