fix(collision): treat case/whitespace-variant identities as one person

Vision reports a display name ("Karti") while the git watcher reports a handle ("karti"); the detectors compared engineerId case-sensitively, so the same human collided with themselves. Canonicalize identity at the decision point in both the file and research detectors, keeping the display-cased name for the card.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/src/collision/detector.ts

@@ -19,6 +19,15 @@ function fileKey(raw?: string): string | undefined {
   return base.toLowerCase();
 }
 
+/**
+ * Canonicalize an engineer identity for case/whitespace-insensitive matching.
+ * Vision reports a display name ("Karti") while the git watcher reports a handle
+ * ("karti"); without this the same human collides with themselves.
+ */
+function canonicalName(raw: string): string {
+  return raw.trim().toLowerCase();
+}
+
 interface Touch {
   engineerId: string;
   unpushed: boolean;
@@ -64,8 +73,15 @@ export function detectCollisions(
 
   const out: Collision[] = [];
   for (const [, touches] of byFile) {
-    const engineers = [...new Set(touches.map((t) => t.engineerId))];
+    // Distinct PEOPLE, case/whitespace-insensitive — one display name per person.
-    if (engineers.length < 2) continue; // need two distinct people on one file
+    // Vision "Karti" and git "karti" are the same human, not a collision.
+    const byPerson = new Map<string, string>(); // canonical id -> display name
+    for (const t of touches) {
+      const id = canonicalName(t.engineerId);
+      if (id && !byPerson.has(id)) byPerson.set(id, t.engineerId);
+    }
+    if (byPerson.size < 2) continue; // need two distinct people on one file
+    const engineers = [...byPerson.values()];
 
     const anyUnpushed = touches.some((t) => t.unpushed) || github.unpushed === true;
     if (!anyUnpushed) continue; // the crux GitHub alone cannot answer

backend/src/collision/research.ts

@@ -24,6 +24,12 @@ function stripGitPrefix(raw: string): string {
   return raw.trim().replace(/^(\?\?|[MADRCU!]{1,2})\s+/, '');
 }
 
+/** Case/whitespace-insensitive identity so vision "Karti" and git "karti" are
+ *  recognized as the same person and never flagged researching-vs-editing self. */
+function canonicalName(raw: string): string {
+  return raw.trim().toLowerCase();
+}
+
 function fileStem(raw: string): string {
   const base = stripGitPrefix(raw).split(/[\\/]/).pop()?.trim().toLowerCase() ?? '';
   return base.replace(/\.[^.]+$/, '');
@@ -104,7 +110,7 @@ export async function detectResearchOverlaps(
     const researchText = [topic, source].filter(Boolean).join(' ');
 
     for (const editor of editorFiles) {
-      if (editor.engineerId === researcher.engineerId) continue;
+      if (canonicalName(editor.engineerId) === canonicalName(researcher.engineerId)) continue;
 
       const stem = fileStem(editor.file);
       if (!stem) continue;