refactor(project): apply simplify review

- Fix prunable parser to match 'prunable <reason>' lines, not just bare 'prunable'.
- Parallelize Effect.forEach in Worktree.list with concurrency: 'unbounded' to match the rest of the file.
- Simplify the experimental worktree GET handler to use Effect.fn(fn, Effect.map(...)).
- Drop unused isProjectList/isProjectUpdate type guards and the unknown-cast set/setBootStore wrappers in global-sync; expose setGlobalStore directly.
- Centralize project worktree mutations as globalSync.project.addWorktree / removeWorktree, replacing three near-duplicate produce blocks in pages/layout.tsx and prompt-input/submit.ts. Use pathKey for dedup in all sites.
- Cast project.updated event properties as Project (not ProjectInfo) and seed worktrees: [] on insert.
- Extract projectDirectories(project) helper in pages/layout/helpers.ts; use at six call sites that built [project.worktree, ...(project.worktrees ?? [])] inline.