feat: add codegraph auto-init-repos command

[CagesThrottleUs]

What this adds

A new codegraph auto-init-repos command that installs a global git template hook so every subsequent git clone or git init automatically runs codegraph init and codegraph index — no manual step required per repo.

# Install once — all future clones auto-initialize
codegraph auto-init-repos

# Undo
codegraph auto-init-repos --remove

How it works

Git copies the contents of ~/.git-templates/ into every new repo's .git/ at clone/init time. The command writes a post-checkout hook into that directory. On first checkout after a clone, the hook:

1. Checks if .codegraph/ exists
2. If not → runs codegraph init . + codegraph index, and appends .codegraph/ to .gitignore (idempotent via grep -qxF)
3. If yes → runs codegraph sync in the background (non-blocking)

The hook is guarded by command -v codegraph so it no-ops silently on machines where CodeGraph is not installed. It also checks $3 = 1 to skip file-level git checkout -- file calls and only fire on actual branch switches/clones.

Platform scope: macOS, Linux, Git for Windows (MINGW). Native Windows cmd/PowerShell is out of scope.

Code structure

src/sync/hook-utils.ts          # NEW — shared primitives (stripMarkerBlock, isEffectivelyEmpty, chmodExecutable)
src/sync/git-hooks.ts           # REFACTORED — now imports from hook-utils (no behavior change)
src/sync/global-hooks.ts        # NEW — resolveTemplateDir, installGlobalAutoInitHook, removeGlobalAutoInitHook
src/bin/auto-init-repos-action.ts # NEW — extracted CLI action handler (clack injected for testability)
src/bin/codegraph.ts            # MODIFIED — registers the auto-init-repos command

Tests

53 new tests across 3 test files, all passing. Full suite: 770 tests, 0 failures.

File	Tests	Coverage
__tests__/hook-utils.test.ts	14	stripMarkerBlock (6), isEffectivelyEmpty (6), chmodExecutable (2)
__tests__/global-hooks.test.ts	22	resolveTemplateDir, install/remove/status, idempotency, git config isolation
__tests__/auto-init-repos-cli.test.ts	12	install path, remove path, error handling
__tests__/git-hooks.test.ts	7	existing tests — all still pass after refactor

Tests use GIT_CONFIG_GLOBAL env var isolation so they never touch the real ~/.gitconfig.

Design spec

Full requirements, test traceability matrix, and design decisions are in:
docs/superpowers/specs/2026-05-22-auto-init-repos-design.md

Every line of code maps back to a named requirement (REQ-HU-xx, REQ-GL-xx, REQ-CLI-xx). Every requirement has at least one test ID.

Install / remove behavior

Scenario	Result
First run	Creates ~/.git-templates/hooks/post-checkout, sets git config --global init.templateDir if not already set
Re-run (idempotent)	Detects byte-identical block → reports "Already installed", no file write
Existing user hook	Appends our block after user content, preserves everything else
--remove with shared hook	Strips only our marker block, preserves user content
--remove when only ours	Deletes the file entirely
--remove never	Touches git config init.templateDir