docs: add CLAUDE.md with fork context and drift policy

Author: maxfindel

CLAUDE.md

@@ -0,0 +1,43 @@
+# spec-kit — Fellowship Fork
+
+This is a fork of [github/spec-kit](https://github.com/github/spec-kit), intentionally diverged. We maintain our own flavor: tighter line limits, no prose, bash scripts included.
+
+## Fork Status
+
+- **Upstream**: `github/spec-kit`
+- **Commits behind upstream**: 252+ (intentional — we diverged significantly)
+- **Do NOT auto-merge upstream** — changes must be cherry-picked manually and reviewed
+
+## Consumer Repos
+
+These repos install speckit commands from this fork (not from upstream):
+
+- `fellowship-dev/booster-pack`
+- `fellowship-dev/rails-backend`
+- `fellowship-dev/inbox-angel-worker`
+- `fellowship-dev/mtg-lotr`
+- Clapes repos
+
+Consumer repos copy commands into `.claude/commands/` (e.g., `speckit.specify.md`, `speckit.plan.md`).
+
+## Drift & Updates
+
+- **Drift is checked weekly** by the tooling crew (every Monday at 1am CLT)
+- The sync task compares installed command SHAs against this repo's HEAD
+- If a consumer repo is drifted, the sync task opens a PR to update it
+- To update a consumer repo manually: copy updated command files into `.claude/commands/`
+
+## Upstream Cherry-Picks
+
+- The tooling crew also checks `github/spec-kit` weekly for potentially relevant commits
+- A GitHub issue is created on this repo listing recommendations
+- Cherry-picks are **manual only** — review carefully before applying
+- Never auto-merge from upstream
+
+## What Changed vs Upstream
+
+- Commands cut ~80%: original ~1,400 lines → this fork ~250 lines
+- Strict line limits: spec ≤50, plan ≤50, tasks ≤40
+- No prose: tasks are checkboxes, specs are bullets, plans are tables
+- Bash scripts included for branch creation and plan setup
+- Generic constitution template included