Polish demo readability and summary fallback

Co-authored-by: Codex <codex@openai.com>

app.py

@@ -64,27 +64,27 @@ CSS = """
 }
 
 .score-card {
-  background: white;
+  background: #ffffff !important;
   border: 1px solid var(--line);
   border-radius: 8px;
   padding: 12px;
 }
 
 .score-label {
-  color: var(--muted);
+  color: #475569 !important;
   font-size: 12px;
   text-transform: uppercase;
 }
 
 .score-value {
-  color: var(--ink);
+  color: #111827 !important;
   font-size: 24px;
   font-weight: 700;
   margin-top: 2px;
 }
 
 .diff-wrap {
-  background: white;
+  background: #ffffff !important;
   border: 1px solid var(--line);
   border-radius: 8px;
   overflow: hidden;
@@ -123,33 +123,40 @@ CSS = """
 }
 
 .line-code {
+  background: #ffffff;
+  color: #111827;
   white-space: pre-wrap;
   overflow-wrap: anywhere;
   padding: 3px 10px;
 }
 
+.line.ctx .line-code {
+  background: #ffffff !important;
+  color: #334155 !important;
+}
+
 .line.add .line-code {
-  background: var(--add-bg);
-  color: var(--add-ink);
+  background: var(--add-bg) !important;
+  color: var(--add-ink) !important;
 }
 
 .line.del .line-code {
-  background: var(--del-bg);
-  color: var(--del-ink);
+  background: var(--del-bg) !important;
+  color: var(--del-ink) !important;
 }
 
 .finding {
   border-top: 1px solid var(--line);
   padding: 10px 12px 12px 66px;
-  background: #fff7ed;
+  background: #fff7ed !important;
 }
 
 .finding.critical {
-  background: #fff1f2;
+  background: #fff1f2 !important;
 }
 
 .finding.nitpick {
-  background: #f8fafc;
+  background: #f8fafc !important;
 }
 
 .badge {
@@ -174,20 +181,20 @@ CSS = """
 }
 
 .finding-body {
-  color: var(--ink);
+  color: #111827 !important;
   margin-top: 6px;
 }
 
 .suggestion {
-  color: #334155;
+  color: #334155 !important;
   margin-top: 5px;
 }
 
 .empty-state {
-  background: white;
+  background: #ffffff !important;
   border: 1px dashed var(--line);
   border-radius: 8px;
-  color: var(--muted);
+  color: #475569 !important;
   padding: 18px;
 }
 
@@ -519,11 +526,15 @@ def summarize_with_model(
     hf_token: gr.OAuthToken | None = None,
 ) -> str:
     if not enabled:
-        return "Model summary disabled. Deterministic review completed locally in the app process."
+        return summarize_deterministic(files, findings, prefix="Deterministic review complete.")
 
     token = hf_token.token if hf_token else os.getenv("HF_TOKEN")
     if not token:
-        return "Model summary skipped: sign in with Hugging Face OAuth or set HF_TOKEN."
+        return summarize_deterministic(
+            files,
+            findings,
+            prefix="Mellum summary needs Hugging Face OAuth or HF_TOKEN; showing deterministic summary.",
+        )
 
     compact_diff = "\n".join(
         f"{file.path}\n"
@@ -566,7 +577,33 @@ def summarize_with_model(
         )
         return response.choices[0].message.content or "Model returned an empty summary."
     except Exception as exc:  # The app must stay demoable when endpoints are unavailable.
-        return f"Model summary unavailable from {DEFAULT_MODEL}: {exc}"
+        return summarize_deterministic(
+            files,
+            findings,
+            prefix=f"Model summary unavailable from {DEFAULT_MODEL}: {exc}",
+        )
+
+
+def summarize_deterministic(files: list[FileDiff], findings: list[Finding], prefix: str) -> str:
+    hunk_count = sum(len(file.hunks) for file in files)
+    counts = {
+        "critical": sum(item.severity == "critical" for item in findings),
+        "warning": sum(item.severity == "warning" for item in findings),
+        "nitpick": sum(item.severity == "nitpick" for item in findings),
+    }
+    top_findings = findings[:3]
+    bullets = [
+        f"- Reviewed {len(files)} files and {hunk_count} hunks.",
+        f"- Found {counts['critical']} critical, {counts['warning']} warning, and {counts['nitpick']} nitpick findings.",
+    ]
+    for finding in top_findings:
+        location = f"{finding.file}:{finding.line}" if finding.line else finding.file
+        bullets.append(f"- {finding.severity.title()} in `{location}`: {finding.comment}")
+
+    if not findings:
+        bullets.append("- No high-signal risks matched the current deterministic rules.")
+
+    return prefix + "\n\n" + "\n".join(bullets)
 
 
 def finding_to_dict(finding: Finding) -> dict[str, Any]: