fix: downgrade body-only fallback to COMMENT and handle own-PR line-resolution retry in PR review buffer

[Copilot]

*-miner bot PRs (where the workflow identity == PR author) hard-failed safe_outputs with 422 "Can not request changes on your own pull request" because two fallback paths in pr_review_buffer.cjs didn't account for the self-review restriction.

Root causes

Bug 1 — body-only fallback preserved original event
When createReview failed with "Line could not be resolved", the body-only retry kept requestParams.event (REQUEST_CHANGES/APPROVE), hitting a second 422 on own PRs.

Bug 2 — own-PR COMMENT retry had no further fallback
The existing own-PR handler retried with event=COMMENT but still included inline comments. If those comments referenced unresolvable lines, the retry threw and the catch block returned a hard failure instead of degrading to body-only.

Changes

• pr_review_buffer.cjs
  • Body-only fallback ("Line could not be resolved" path): explicitly set bodyOnlyParams.event = "COMMENT". Once all inline comments are stripped this path is already degraded; COMMENT is always safe and avoids the own-PR 422.
  • Own-PR COMMENT retry catch: when the retry fails due to "Line could not be resolved" or "Path could not be resolved", fall back to a body-only COMMENT review (with unanchored comments appended to the body) before returning failure.

REQUEST_CHANGES + comments
  → 422 "Can not request changes on your own PR"
    → COMMENT + comments
      → "Line could not be resolved"           ← previously hard-failed here
        → COMMENT (body-only, comments in body) ← new

• pr_review_buffer.test.cjs — 5 new tests covering the two fix paths, their failure branches, and the partial-anchor-then-own-PR-body-only chain.

• Fixes [aw-failures] [aw-fix] P1: PR Code Quality Reviewer — safe-outputs review 422 "can not request changes on your own PR" on *-mine [Content truncated due to length] #47390

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