Stand up git-worktree-poi as a Rust binary repo to replace the bash worktree pruner

## Summary

Stand up [`alunduil/git-worktree-poi`](https://github.com/alunduil/git-worktree-poi) — a Rust CLI that replaces the chezmoi-managed bash `dot_local/bin/executable_git-worktree-poi` (now ~633 lines) driving worktree classification, the gh-poi-style report, and pruning in the pair workflow. This is the cross-repo planning artifact for the project: decisions, the single new repo to create, and the bootstrap milestone that closes it. Supersedes the deferral in [alunduil-chezmoi ADR 0001](https://github.com/alunduil/alunduil-chezmoi/blob/main/docs/adr/0001-keep-git-worktree-poi-in-bash.md), re-evaluated in [alunduil-chezmoi#205](https://github.com/alunduil/alunduil-chezmoi/issues/205) and recorded as [alunduil-chezmoi ADR 0002](https://github.com/alunduil/alunduil-chezmoi/blob/main/docs/adr/0002-port-git-worktree-poi-to-rust.md).

Bounded against the other pair-workflow artifact, #155 (`zellij-claude-pair`): that plugin owns the in-session surface (repo picker, status widgets); this CLI runs headless under a systemd timer and the `git-poi-all` sweeper, outside any zellij session.

## Background and motivation

ADR 0001 (2026, alunduil-chezmoi) kept the pruner in bash and deferred a rewrite behind explicit triggers. Two have since fired:

- **Size.** The ADR cited 234 lines as the evidence it was small enough for bash. The script is now 633 lines — 2.7×, well past the ADR's own "~100 lines of bash addition" trigger.
- **GraphQL batching.** ADR 0001 named [alunduil-chezmoi#147](https://github.com/alunduil/alunduil-chezmoi/issues/147) (batched PR-state lookup) as a revisit trigger; it landed as bash in [alunduil-chezmoi#154](https://github.com/alunduil/alunduil-chezmoi/issues/154) via a `gh api graphql` heredoc + `jq` — exactly the "more jq/heredoc surgery than a rewrite would cost" trigger.

ADR 0001 picked Go on a `gh-poi`-extension framing, but the tool never became a `gh` extension — it's a standalone bin. The pair workflow's other tooling has since standardized on Rust (#155, which absorbed the separately-planned `git-repo-picker` #54 and `zellij-git-status` #26), and rustup is already bootstrapped in chezmoi. So the port goes to Rust, aligning the toolchain.

## Strategic decisions

| Decision | Choice | Rationale |
|---|---|---|
| Binary runtime | Rust → native CLI | Matches the pair workflow's other Rust tooling (#155); rustup bootstrapped in chezmoi. Supersedes ADR 0001's Go pick |
| License | MIT | Matches surrounding ecosystem |
| Versioning | SemVer 2.0.0 | Standard |
| Changelog | Keep a Changelog 1.1.0 | Manual; no auto-gen day 1 |
| Distribution | GitHub Releases (precompiled per platform) | Mirrors `script/install/{gcx,act,lazygit}` in chezmoi |
| Platforms | linux-x86_64, linux-aarch64 | Covers Crostini host; expand on request |
| Data sources | `git`, `gh`/`octocrab` | `git` for worktree/branch state; batched GraphQL for PR state (replaces chezmoi#154's jq/heredoc) |
| Color | Rust color crate (`owo-colors`/`anstream`) | Replaces ADR 0001's `tput`/ANSI in `print_section` |

## Repository inventory

| Status | Repository | Purpose | Notes |
|---|---|---|---|
| ✅ created | [`alunduil/git-worktree-poi`](https://github.com/alunduil/git-worktree-poi) | The CLI binary | Created out-of-band, adopted into Terraform in #263 |
| ✅ exists | `alunduil/alunduil-chezmoi` | Binary consumer | `script/install/` pin, bin removal, systemd `ExecStart` swap, bats removal, `git-poi-all` contract — [alunduil-chezmoi#295](https://github.com/alunduil/alunduil-chezmoi/issues/295) |
| ✅ exists | `alunduil/alunduil-infrastructure` | Cross-repo planning | This issue |

## Architecture

Issue references below are alunduil-chezmoi, where the bash pruner lives.

- **Worktree classification** — canonical-path resolution ([chezmoi#138](https://github.com/alunduil/alunduil-chezmoi/issues/138)), namespaced `/worktree/` branches ([chezmoi#110](https://github.com/alunduil/alunduil-chezmoi/issues/110)), in-use guard ([chezmoi#140](https://github.com/alunduil/alunduil-chezmoi/issues/140)), empty-worktree safe path ([chezmoi#141](https://github.com/alunduil/alunduil-chezmoi/issues/141)).
- **PR-state lookup** — one batched GraphQL per repo (the [chezmoi#154](https://github.com/alunduil/alunduil-chezmoi/issues/154) logic, in a typed language; `octocrab` or `gh api graphql` shell-out).
- **gh-poi-style report** — color, single-line rows, dimmed metadata, progress markers ([chezmoi#177](https://github.com/alunduil/alunduil-chezmoi/issues/177), [chezmoi#184](https://github.com/alunduil/alunduil-chezmoi/issues/184)).
- **Prune verbs** — merged / gone-upstream, empty-no-PR; `NAME` targeting + `--force` ([chezmoi#215](https://github.com/alunduil/alunduil-chezmoi/issues/215) parity).
- **Scheduling** — invoked by the `git-worktree-poi.timer` systemd user unit ([chezmoi#273](https://github.com/alunduil/alunduil-chezmoi/issues/273)); consumer keeps the timer, swaps `ExecStart` to the binary.
- **Sweeper contract** — `git-poi-all` ([chezmoi#253](https://github.com/alunduil/alunduil-chezmoi/issues/253)) shells `git-worktree-poi` across clones; keep the CLI stable or co-port (open question).

## Milestones to 1.0.0

**M0 — Repo bootstrap.** README/CONTRIBUTING/CHANGELOG/SECURITY; Cargo + `clap` hello-world; CI (fmt, clippy, test, cross-compile linux-{x86_64,aarch64}, `cargo deny`); Renovate (`config:best-practices`, pre-commit manager); templates + labels; first tagged `v0.0.1` (empty CLI, proves CI+release). *Exit:* binary downloads from Releases on both targets, runs `--version`, exits 0. **Tracked by this issue — the remaining work.**

**M1 — Pruner parity (0.1.0).** [git-worktree-poi#1](https://github.com/alunduil/git-worktree-poi/issues/1). Worktree enumeration + classification; gh-poi-style report; prune verbs; `NAME` + `--force`; bats → cargo test for pure logic, integration tests for git/gh paths. *Exit:* behaviour parity with the chezmoi bash pruner on the same host.

**M2 — Typed PR-state batching (0.2.0).** [git-worktree-poi#2](https://github.com/alunduil/git-worktree-poi/issues/2). Replace the chezmoi#154 `gh api graphql` heredoc + `jq` with typed batched lookup (`octocrab` or structured `gh` shell-out). *Exit:* one batched query per repo; no per-branch round-trips.

**M3 — Cut 1.0.0.** [git-worktree-poi#3](https://github.com/alunduil/git-worktree-poi/issues/3). Version bump, CHANGELOG release section, `v1.0.0` tag, both platform artifacts, and a documented CLI surface for the sweeper and the systemd unit to pin against. *Exit:* `v1.0.0` released and consumable.

The chezmoi-side swap — `script/install/git-worktree-poi` download-and-verify, `dot_local/bin/executable_git-worktree-poi` removed, `git-worktree-poi.service` `ExecStart` repointed, `git-poi-all` contract preserved, `test/git_worktree_poi.bats` deleted — lives in [alunduil-chezmoi#295](https://github.com/alunduil/alunduil-chezmoi/issues/295), blocked by M3. The consumer changes stay in the repo that owns those files rather than being tracked twice.

## CI/CD, release, Renovate, security

No Rust repo in the org is bootstrapped yet — `zellij-claude-pair` (#155) is still LICENSE-only, and `git-repo-picker` (#54) was closed without a repo — so M0 writes this blueprint rather than copying one: `ci.yml` (fmt/clippy/test/build-matrix/`cargo deny`, all required, draft PRs); `release.yml` on tag `v*` (per-platform tarballs + sha256, notes from CHANGELOG); manual version bump; Renovate `config:best-practices` + pre-commit manager + grouped `rust-lang/*`; Dependabot alerts, secret scanning + push protection, private vuln reporting. Repository settings are declared in `terraform/alunduil/repositories.tf`, not clicked in.

## Open questions

1. **Color crate** — `owo-colors` vs `anstream`/`yansi`. Decide before M1 (restated in git-worktree-poi#1).
2. **PR-state client** — `octocrab` vs `gh api graphql` shell-out. Decide before M2 (restated in git-worktree-poi#2).
3. **`git-poi-all`** — co-port to Rust, or keep the bash sweeper calling the new binary? Decide before M3 (restated in git-worktree-poi#3).
4. **Directory input** — positional arguments vs configuration for the worktree directories to scan. Raised in git-worktree-poi#1; bears on the sweeper contract and the systemd unit's invocation.

## Out of scope (deliberately)

- In-session repo picking and status widgets — #155 handles those.
- Shared cache/report crate with `zellij-claude-pair` — extract on rule of three.
- Non-GitHub forges, multi-VCS (jj/hg), telemetry.

## Done when

- [x] Repo created at [`alunduil/git-worktree-poi`](https://github.com/alunduil/git-worktree-poi) (MIT), adopted into Terraform (#263)
- [ ] M0 bootstrap complete (CI, release, templates, tagged `v0.0.1`)
- [x] Tracking issues for M1–M3 opened in the new repo ([#1](https://github.com/alunduil/git-worktree-poi/issues/1), [#2](https://github.com/alunduil/git-worktree-poi/issues/2), [#3](https://github.com/alunduil/git-worktree-poi/issues/3))
- [x] This issue updated with links to the new repo and per-milestone issues
- [x] alunduil-chezmoi consumer issue filed ([alunduil-chezmoi#295](https://github.com/alunduil/alunduil-chezmoi/issues/295)), blocked-by this issue