worktree-kitlisted

One worktree per issue. State lives in `$PDKIT_HOME`, keyed by issue, so every tree sees the same state rather than its own copy — that is what makes parallel work safe here rather than merely possible. ``` pdkit worktree create --issue <n> [--branch <b>] [--ref <r>] pdkit worktree list pdkit worktree remove --issue <n> [--force] ``` Trees go beside the fork (`worktrees.root`, default `../pd-worktrees`), never inside it: a checkout under the repository shows up in `git status` and, eventually, in a pull request. `.env` and anything else in `worktrees.copy_files` is copied in on creation. The pnpm store is global, so a fresh tree installs by hardlinking rather than downloading — but `node_modules` is still per tree and still costs minutes on this workspace. That is why the verification tree (`verify-DESKTOP-<n>`) is reused between runs instead of recreated. ## What is per tree and what is not - **Per tree**: the checkout, `node_modules`, and the *active task* — the pointer `pdkit task start` writes is keyed by working tree, so two trees can run two tasks of the same issue without either hook guarding the wrong files. - **Shared**: everything under `$PDKIT_HOME` — state, plan, receipts, the slice graph, the journal, and consent tokens. ## Removal `pdkit worktree remove` refuses while the tree holds a branch that has not landed in `main`. Removing it takes the commits with it and leaves nothing that says it happened, so `--force` is the way to say you meant to aband