fix: address swarm review of consensus consolidation (PR #17)

From PR #17's own adversarial review (now running on the Phase-1 image — note
the much cleaner, less-fragmented findings). Graded in gadfly-reports.

- Never lose output (advisory invariant): run.sh writes a stub findings file
  when a model fails/skips under consolidation, so a failed model still shows
  (as failed) and an all-models-fail run still posts a comment.
- Errored models excluded from the agreement denominator (modelFindings.Errored
  + allErrored); shown folded as "reviewer failed", not counted as clean.
- Sliding cluster window: span [line,maxLine] widened by tolerance on both
  edges, so chains of nearby findings merge instead of splitting (fixes
  agreement under-counting). Clustering is now per-file (no global O(n²) scan).
- Lone-finding headline threshold raised high -> critical (matches the docs);
  only consensus or a lone critical earns the headline, the rest fold.
- findings_file_for appends a cksum so foo:bar vs foo/bar can't collide.
- mdCell escapes the location cell + neutralizes backticks (table-injection);
  "No material issues" no longer shown when folded findings exist.
- Removed dead cluster.detail; named findingRef type; single partition/agreed
  pass; writeFindingsOut MkdirAll; captureStdout defer-restore + close.

Tests added: sliding-window chain merge, errored-denominator exclusion, lone
HIGH folds. gofmt/vet/bash -n clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

scripts/run.sh

@@ -214,6 +214,16 @@ esac
 # --- assemble + post final comment (with run time) --------------------------
 ELAPSED="$(( $(date +%s) - START_TS ))"
 DUR="$(fmt_duration "$ELAPSED")"
+
+# Consolidating: the binary writes its findings file on success. If it failed or
+# was skipped (no file, or an empty one), write a stub so this model still shows
+# up in the consensus (as failed) and an all-models-fail run still posts a
+# comment — never silently drop a model or the whole review.
+if [ "$CONSOLIDATE" = "1" ] && [ -n "${GADFLY_FINDINGS_OUT:-}" ] && [ ! -s "${GADFLY_FINDINGS_OUT}" ]; then
+  jq -n --arg model "$MODEL" --arg provider "$MODEL_PROVIDER" --arg md "$REVIEW" \
+    '{model:$model, provider:$provider, verdict:"reviewer failed", errored:true, markdown:$md, findings:[]}' \
+    > "${GADFLY_FINDINGS_OUT}" 2>/dev/null || true
+fi
 # When consolidating, the binary has written this model's findings to
 # GADFLY_FINDINGS_OUT; the consensus comment is posted by entrypoint.sh after the
 # whole swarm finishes, so this model posts no comment of its own.