refactor(pipeline): ignore specs/plans via project-local docs/.gitignore

Replace the global ~/.config/git/ignore mechanism with a committed,
per-project docs/.gitignore whose entries `specs/` and `plans/` are
relative to docs/. The ignore now travels with each repo instead of
living in the user's global excludes.

specify (Step 3) and planner (intro) create docs/.gitignore on demand
if a project has not set it up yet, so a spec/plan can never become
committable. conventions.md § File layout is the single source; the
onboarding fragment tells a new project to set it up.

The global ~/.config/git/ignore block is removed separately (it is
outside this repo).

docs/conventions.md

@@ -28,13 +28,17 @@ elsewhere is the rare exception and states the override in its
 `CLAUDE.md` project facts.
 
 Both directories are **git-ignored** — their contents are transient
-working files, never committed (see § Lifecycle). The plugin ignores
-them **globally**: `docs/specs/` and `docs/plans/` live in the user's
-global git excludes (`~/.config/git/ignore`, the XDG default that
-applies to every repo), next to the other plugin-wide ignores. One
-entry set covers every project — no per-project `.gitignore` line is
-needed, though a project MAY add its own if it wants the ignore to
-travel with the repo.
+working files, never committed (see § Lifecycle). The ignore is
+**project-local**: each project commits a `docs/.gitignore` whose two
+entries, `specs/` and `plans/`, are relative to `docs/` and so match
+`docs/specs/` and `docs/plans/`. That `docs/.gitignore` is the one
+committed thing — it travels with the repo; the spec and plan files it
+covers never are. It is created once (whichever skill first writes a
+working file — `specify`, or `planner` on a direct tidy dispatch —
+creates it if absent) and committed like any other repo file, after
+which both directories are invisible to git for every future cycle. A
+new project sets this up as part of adopting the plugin
+(`../templates/CLAUDE.md.fragment`).
 
 ## Lifecycle
 

planner/SKILL.md

@@ -17,8 +17,11 @@ into bites small enough that a subagent can execute one in
 
 Plans live under `docs/plans` with the fixed name shape
 `slug.md` — a short kebab-case topic slug, no numeric prefix (see
-`docs/conventions.md` § Naming). `docs/plans` is git-ignored; the plan
-is a working file, never committed. The header references the parent spec. The plan
+`docs/conventions.md` § Naming). `docs/plans` is git-ignored via the
+project's committed `docs/.gitignore`; on a direct tidy dispatch that
+skipped `specify`, create that file first if it does not yet ignore
+`plans/` (`docs/conventions.md` § File layout). The plan is a working
+file, never committed. The header references the parent spec. The plan
 decomposes work into tasks; each task is the unit of review
 (spec-compliance and quality gates inside `implement`), not
 the unit of commit. Commits are an orchestrator-only decision

specify/SKILL.md

@@ -270,8 +270,11 @@ it as a target, not verified fact.
 
 Path: under `docs/specs`, named `slug.md` per the fixed naming
 convention (see `docs/conventions.md` § Naming) — a short kebab-case
-topic slug, no numeric prefix. The directory is git-ignored; the spec is
-created there and never `git add`'d.
+topic slug, no numeric prefix. The directory is git-ignored via the
+project's committed `docs/.gitignore`; if that file does not yet ignore
+`specs/`, create it first (`docs/conventions.md` § File layout) so the
+spec can never be committable. The spec is created under `docs/specs` and
+never `git add`'d.
 
 Structure:
 

templates/CLAUDE.md.fragment

@@ -68,15 +68,17 @@ Two rules govern who touches git history and how:
 ## Spec/plan artefacts are ephemeral
 
 `docs/specs/` and `docs/plans/` hold only the active cycle's spec and
-plan, and they are **git-ignored** — never committed (the plugin ignores
-them globally via `~/.config/git/ignore`; a project may add its own
-`.gitignore` entry instead). Each is a working file: present on disk for
-its own cycle, read across sessions from the working tree, and
-shell-`rm`'d at cycle close by `audit` — never `git rm`'d, since it was
-never tracked, so no git-history copy survives. The durable record of a
-past cycle is the design ledger only, and no durable artefact cites a
-spec/plan by number or path (see `~/dev/skills/docs/conventions.md`
-§ Lifecycle).
+plan, and they are **git-ignored** — never committed. This repo carries
+a committed `docs/.gitignore` with the two entries `specs/` and `plans/`
+(relative to `docs/`); that ignore file is the only committed part — the
+spec and plan files it covers never are. If `docs/.gitignore` is missing
+when the first working file is written, the writing skill creates it.
+Each spec / plan is a working file: present on disk for its own cycle,
+read across sessions from the working tree, and shell-`rm`'d at cycle
+close by `audit` — never `git rm`'d, since it was never tracked, so no
+git-history copy survives. The durable record of a past cycle is the
+design ledger only, and no durable artefact cites a spec/plan by number
+or path (see `~/dev/skills/docs/conventions.md` § Lifecycle).
 
 ## Design rationale ≠ implementation effort