fix(project-name): use parent/worktree composite so observations don't cross worktrees

Revert of #1820 behavior. Each worktree now gets its own bucket:
- In a worktree, primary = `parent/worktree` (e.g. `claude-mem/dar-es-salaam`)
- In a main repo, primary = basename (unchanged)
- allProjects is always `[primary]` — strict isolation at query time

Includes a one-off maintenance script (scripts/worktree-remap.ts) that
retroactively reattributes past sessions to their worktree using path
signals in observations and user prompts. Two-rule inference keeps the
remap high-confidence:
  1. The worktree basename in the path matches the session's current
     plain project name (pre-#1820 era; trusted).
  2. Or all worktree path signals converge on a single (parent, worktree)
     across the session.
Ambiguous sessions are skipped.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/utils/project-name.ts

@@ -58,21 +58,24 @@ export function getProjectName(cwd: string | null | undefined): string {
  * Project context with worktree awareness
  */
 export interface ProjectContext {
-  /** Canonical project name for writes/queries (parent repo in worktrees) */
+  /** Canonical project name for writes/queries; `parent/worktree` when in a worktree */
   primary: string;
   /** Parent project name if in a worktree, null otherwise */
   parent: string | null;
   /** True if currently in a worktree */
   isWorktree: boolean;
-  /** All projects to query: [primary] for main repo, [parentRepo, worktreeName] for worktree */
+  /** Projects to query — always `[primary]` so observations don't cross worktrees */
   allProjects: string[];
 }
 
 /**
  * Get project context with worktree detection.
  *
- * When in a worktree, returns both the worktree project name and parent project name
- * for unified timeline queries.
+ * Each worktree is its own bucket. When in a worktree, `primary` is the
+ * composite `parent/worktree` (e.g. `claude-mem/dar-es-salaam`) so worktrees
+ * are uniquely identified and grouped under their parent project without
+ * mixing observations across them. In the main repo, `primary` is just the
+ * project basename.
  *
  * @param cwd - Current working directory (absolute path)
  * @returns ProjectContext with worktree info
@@ -88,14 +91,12 @@ export function getProjectContext(cwd: string | null | undefined): ProjectContex
   const worktreeInfo = detectWorktree(expandedCwd);
 
   if (worktreeInfo.isWorktree && worktreeInfo.parentProjectName) {
-    // In a worktree: use parent project name as primary so observations
-    // are stored under the same project as the main repo (#1081, #1500, #1819)
-    const allProjects = Array.from(new Set([worktreeInfo.parentProjectName, cwdProjectName]));
+    const composite = `${worktreeInfo.parentProjectName}/${cwdProjectName}`;
     return {
-      primary: worktreeInfo.parentProjectName,
+      primary: composite,
       parent: worktreeInfo.parentProjectName,
       isWorktree: true,
-      allProjects
+      allProjects: [composite]
     };
   }