fix: widen handoff detection context window beyond single-line sentence extraction

Remove \n from sentence boundary regexes in extractSentence so markdown
newlines no longer truncate the context window. This fixes handoff chip
detection when specialist names and intent phrases span multiple lines
(e.g., markdown headings followed by body text). Caps extracted sentences
at 500 chars to prevent runaway matching.

Author: marian2js

apps/desktop/src/features/chat/lib/handoff-detector.ts

@@ -65,23 +65,28 @@ function generateDeterministicId(specialistId: string, reason: string): string {
 }
 
 function extractSentence(text: string, matchIndex: number): string {
-  // Find sentence boundaries around the match position
+  // Find sentence boundaries around the match position.
+  // Use only . ! ? as sentence terminators — NOT \n, which is a
+  // formatting character in markdown and would break cross-line detection.
   const beforeText = text.slice(0, matchIndex);
   const afterText = text.slice(matchIndex);
 
   // Find sentence start (look backwards for . ! ? or start of text)
-  const sentenceStartMatch = beforeText.match(/(?:.*[.!?\n]\s*)([^.!?\n]*)$/);
+  const sentenceStartMatch = beforeText.match(/(?:.*[.!?]\s*)([^.!?]*)$/);
   const sentenceStart = sentenceStartMatch
     ? matchIndex - sentenceStartMatch[1].length
     : 0;
 
   // Find sentence end (look forwards for . ! ? or end of text)
-  const sentenceEndMatch = afterText.match(/^[^.!?\n]*[.!?\n]?/);
+  const sentenceEndMatch = afterText.match(/^[^.!?]*[.!?]?/);
   const sentenceEnd = sentenceEndMatch
     ? matchIndex + sentenceEndMatch[0].length
     : text.length;
 
-  return text.slice(sentenceStart, sentenceEnd).trim();
+  // Cap at 500 characters to avoid matching the entire message
+  const MAX_SENTENCE_LEN = 500;
+  const raw = text.slice(sentenceStart, sentenceEnd).trim();
+  return raw.length > MAX_SENTENCE_LEN ? raw.slice(0, MAX_SENTENCE_LEN) : raw;
 }
 
 function hasHandoffIntent(sentence: string): boolean {

test/features/chat/lib/handoff-detector.test.ts

@@ -159,6 +159,47 @@ describe("detectHandoffSuggestions", () => {
     });
   });
 
+  describe("markdown-formatted text with cross-line detection", () => {
+    it("detects handoff when specialist name is on a heading line and intent phrase on next line", () => {
+      const text =
+        "## For the Positioning Agent\n**The Positioning Agent could help sharpen messaging based on these gaps.**";
+      const result = detectHandoffSuggestions(text);
+      expect(result.length).toBeGreaterThanOrEqual(1);
+      expect(result[0].specialistId).toBe("positioning");
+      expect(result[0].reason).toContain("could help");
+    });
+
+    it("detects handoff across newlines for Content Agent", () => {
+      const text =
+        "## For the Content Agent\n**The Content Agent could help turn these angles into blog outlines.**";
+      const result = detectHandoffSuggestions(text);
+      expect(result.length).toBeGreaterThanOrEqual(1);
+      expect(result[0].specialistId).toBe("content");
+    });
+
+    it("detects multiple handoffs in markdown-formatted response spanning lines", () => {
+      const text =
+        "## Next Steps\n\n" +
+        "### For the Positioning Agent\n" +
+        "**The Positioning Agent could help sharpen messaging based on these gaps.**\n\n" +
+        "### For the Content Agent\n" +
+        "**The Content Agent could help turn these angles into blog posts.**";
+      const result = detectHandoffSuggestions(text);
+      expect(result.length).toBe(2);
+      const ids = result.map((s) => s.specialistId);
+      expect(ids).toContain("positioning");
+      expect(ids).toContain("content");
+    });
+
+    it("still detects single-line sentences after fix", () => {
+      const result = detectHandoffSuggestions(
+        "The Positioning Agent could help with messaging.",
+      );
+      expect(result.length).toBeGreaterThanOrEqual(1);
+      expect(result[0].specialistId).toBe("positioning");
+    });
+  });
+
   describe("case insensitivity", () => {
     it("handles varied capitalization of specialist names", () => {
       const result = detectHandoffSuggestions(