chore(stamphog): Raise auto-review line ceiling to 1000 (#3246)

Author: charlesvien

tools/pr-approval-agent/README.md

@@ -58,7 +58,7 @@ Deny-list (hard gate)
   │
   ▼
 Size ceiling (hard gate)
-  - >500 lines or >20 files → too large for auto-review
+  - >1000 lines or >20 files → too large for auto-review
   │
   ▼
 Tier classification

tools/pr-approval-agent/gates.py

@@ -525,7 +525,7 @@ def detect_ownership(files: list[str], rules: list[CodeownersRule]) -> dict:
 # ── Tier assignment ──────────────────────────────────────────────
 
 
-MAX_LINES = 500
+MAX_LINES = 1000
 MAX_FILES = 20