feat(prd-1): implement M4b - Forgejo REST comment/review fetching

- Add 3 REST calls to Promise.all for PRs (listComments, listReviews,
  listReviewComments) and 1 for issues (listComments)
- Add mapping helpers: mapRestComments, mapRestReviewComments,
  mapRestReviews (groups inline comments by pull_request_review_id)
- Import and apply TOCTOU filtering (filterCommentsToTriggerTime,
  filterReviewsToTriggerTime) and actor filtering from GitHub fetcher
- Add image processing pipeline via downloadCommentImages (no-op on
  Forgejo due to URL pattern mismatch, architecturally correct)
- Deep-clone reviews before filtering to preserve contextData immutability
- Update test suite: 51 tests covering mapping helpers, full fetch
  flow, TOCTOU filtering, actor filtering, and contextData immutability
- Updated PRD checkboxes for M4b completion

Progress: 44% complete (4/9 milestones) - next: M5 or M3

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/entrypoints/run.ts

@@ -158,10 +158,7 @@ async function run() {
         githubToken = await setupGitHubToken();
       } catch (error) {
         if (error instanceof WorkflowValidationSkipError) {
-          core.setOutput(
-            "skipped_due_to_workflow_validation_mismatch",
-            "true",
-          );
+          core.setOutput("skipped_due_to_workflow_validation_mismatch", "true");
           console.log("Exiting due to workflow validation skip");
           return;
         }