fix(opencode_review): harden _synthesize_summary_fields (none-safe, dedupe emoji map)

pilot/opencode_review.py

@@ -55,7 +55,7 @@ import time
 import urllib.error
 import urllib.request
 
-from ai_review import is_test_path
+from ai_review import _SEVERITY_EMOJI, is_test_path
 
 # Where the factory lives (opencode.json + .opencode/). Default: the pragent
 # repo root (this file is at <root>/pilot/opencode_review.py).
@@ -567,14 +567,6 @@ _LENS_ID_RE = re.compile(r"^[a-z0-9-]{1,32}$")
 SEVERITY_ORDER = ("low", "medium", "high", "critical")
 SEVERITY_RANK = {s: i for i, s in enumerate(SEVERITY_ORDER)}
 
-# Local emoji map for the synthesized walkthrough. Kept separate from
-# `ai_review._SEVERITY_EMOJI` (which also has "trivial"/"info"/"nit") so
-# this stays a small surface for the fallback path.
-_SEVERITY_EMOJI_SUMMARY = {
-    "critical": "🔴", "high": "🔴", "medium": "🟡",
-    "low": "🔵", "trivial": "⚪", "info": "⚪",
-}
-
 
 @_dc.dataclass(frozen=True)
 class ReviewerSpec:
@@ -941,6 +933,10 @@ def _synthesize_summary_fields(
         `is_test_path`, else "No tests for behavioral change in `<path>`."
         pointing at the first non-test path.
     """
+    # None-safe: callers occasionally pass None when the upstream merger
+    # short-circuited. Treat as empty so the for-loop and group-by below
+    # never crash.
+    findings = findings or []
     # walkthrough
     walkthrough: list[str] = []
     if findings:
@@ -954,8 +950,7 @@ def _synthesize_summary_fields(
             )
             problem_lines = (peak.get("problem") or "").splitlines()
             problem = problem_lines[0][:80].strip() if problem_lines else ""
-            emoji = _SEVERITY_EMOJI_SUMMARY.get(
-                peak.get("severity", "low"), "⚪")
+            emoji = _SEVERITY_EMOJI.get(peak.get("severity", "low"), "⚪")
             walkthrough.append(f"`{path}` — {emoji} {problem}")
     else:
         files = changed_paths if changed_paths is not None else changed_files(diff)