Add review summary and run link to PR reviews

[gontzess]

Why

The structured PR review summary can still be hard to scan when a follow-up review has no findings. Reviewers need the summary comment to say what changed, whether prior bot feedback was addressed, and where to inspect the run without restoring the older trusted-code behavior.

What this changes

Adds review_run_url to the pre-fetched PR context and requires the shared prompt to include a run link plus a short Review Summary before the finding sections. Incremental reviews are instructed to mention addressed prior bot feedback in that summary while continuing to use the safe base-checkout and GitHub API diff model.

Validation

• git diff --check
• fetch-pr-context.py compiles with an isolated pycache
• Canary PR flagged a new unsafe type assertion, linked the review run, then updated the same summary after the fix with zero blocking issues and the prior feedback marked addressed