fix(severity): extend badge label set + update SYSTEM_PROMPT

pilot/ai_review.py

@@ -102,7 +102,7 @@ Output STRICT JSON only — no prose, no markdown fences. Shape:
 {
   "findings": [
     {
-      "severity": "critical|high|medium|low",
+      "severity": "critical|high|medium|low|trivial|info",
       "path": "file path exactly as it appears in the diff (`+++ b/` side)",
       "line": <int, the NEW-file line number the issue is on, within the diff>,
       "problem": "one line: what is wrong",
@@ -963,12 +963,19 @@ _SEVERITY_EMOJI = {
     "nit": "⚪",
 }
 
+# Severities whose own name is rendered verbatim (uppercased) in the badge.
+# Anything outside this set falls back to "INFO" so the badge label stays
+# a clean short token regardless of what the model emits.
+_BADGED_SEVERITY_LABELS = frozenset({
+    "critical", "high", "medium", "low", "trivial", "info", "nit",
+})
+
 
 def _severity_badge(severity: str) -> str:
     """Render the severity as emoji + uppercase label (e.g. ``🔴 [HIGH]``)."""
     sev = (severity or "").lower()
     emoji = _SEVERITY_EMOJI.get(sev, "⚪")
-    label = sev.upper() if sev in {"critical", "high", "medium", "low"} else "INFO"
+    label = sev.upper() if sev in _BADGED_SEVERITY_LABELS else "INFO"
     return f"{emoji} [{label}]"