chore: clean buglog.json junk/duplicates, gitignore scratch soak output

buglog.json had two broken auto-detection hook signatures polluting it:
- 207 entries "Missing error handling in X" / fix "Added try/catch block"
  (nonsensical on .md/.capnp files, and C has no try/catch — never a real
  applied fix)
- 452 entries with a literally-empty template ("Significant refactor of "
  with no subject ever filled in) / fix "Rewrote N->M lines"
Removed both (659 total). Also merged 24 legitimate duplicate bug IDs
(re-logged/updated entries sharing an ID) into single entries — kept the
most recent content as primary, unioned tags/related_bugs, summed
occurrences — and stripped noise tags ('auto-detected', 'refactor') that
had leaked onto real entries from a since-merged junk duplicate. Net:
1406 -> 721 entries, verified zero remaining duplicate IDs and zero
remaining junk signatures.

.gitignore: added patterns for the scratch soak-run logs and codegraph.html
this session generated at repo root (already deleted from the tree), and
fixed the ucai-formatter-cache.local.json pattern to match its nested
occurrences (.claude/skills/*/.claude/, src/*/.claude/) instead of only the
repo-root one.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SDWVNQLKxqTVHh42cH7rV3

.gitignore

@@ -26,4 +26,10 @@ graphify-out/
 .codegraph/
 .xce-durability-acked.*
 *.bak
-.claude/ucai-formatter-cache.local.json
+ucai-formatter-cache.local.json
+
+# --- session checkpoint 2026-07-03: scratch soak-run output at repo root ---
+/codegraph.html
+/final_suite_run.log
+/xce-durability-*.log
+/xce-ha-soak*.log