feat(worktree): include parent repo observations in worktree read scope

Worktrees are branches off main; the parent holds the architecture,
decisions, and long-tail history the worktree inherits. Scoping reads
to the worktree alone meant every new worktree started cold on any
question that required prior context.

Expand `allProjects` in a worktree to `[parent, composite]` so reads
pull both. Writes still go through `.primary` (the composite), so
sibling worktrees don't leak into each other.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/utils/project-name.ts

@@ -64,7 +64,9 @@ export interface ProjectContext {
   parent: string | null;
   /** True if currently in a worktree */
   isWorktree: boolean;
-  /** Projects to query — always `[primary]` so observations don't cross worktrees */
+  /** Projects to query for reads. In a worktree: `[parent, composite]` so
+   *  main-repo context flows into every worktree while sibling worktrees stay
+   *  isolated. In the main repo: `[primary]`. Writes always use `.primary`. */
   allProjects: string[];
 }
 
@@ -96,7 +98,7 @@ export function getProjectContext(cwd: string | null | undefined): ProjectContex
       primary: composite,
       parent: worktreeInfo.parentProjectName,
       isWorktree: true,
-      allProjects: [composite]
+      allProjects: [worktreeInfo.parentProjectName, composite]
     };
   }