feat(git): user-level hooks auto-dispatch into <repo>/.githooks/

Inverts the hook delegation model. Previously per-repo hooks required
a project to either (a) write the entire hook themselves and lose the
global signed-commit / agent-author gate, or (b) override
core.hooksPath and write passthrough stubs that exec back to
$HOME/.config/git/hooks/*. Both are ergonomically miserable.

Now: the global hooks at ~/.config/git/hooks/ are *always* the entry
point. Each one calls a shared dispatcher (_dispatch.sh) that runs
<repo>/.githooks/<hookname> if it exists, propagating its exit status,
and then continues with whatever the global hook itself wants to do.
Projects just drop an executable file at .githooks/<name> — no
core.hooksPath, no stubs, no boilerplate. Repos that don't have a
.githooks/ dir keep working exactly as before.

GIT_HOOK_DISPATCHED guards against re-entry so legacy repos using the
old stub-and-exec pattern don't loop. pre-push tees stdin so both the
repo hook and the global ref-list loop see the full push payload.

Adds two new always-no-op global hooks (pre-commit, post-commit)
purely so the dispatch happens for those events too — previously only
commit-msg and pre-push existed globally.

Refactors this dotfiles repo to use the new pattern: drops the
self-delegating .githooks/pre-push stub and removes the per-repo
core.hooksPath override from `just init` (now an idempotent unsetter
to clean up the override from past bootstraps). The remote-dev VM's
home-manager profile symlinks all four hooks plus _dispatch.sh.

1 files changed, 7 insertions, 3 deletions

diff --git a/README.md b/README.md
index 83c621d..0a0c5f3 100644
--- a/README.md
+++ b/README.md
@@ -134,10 +134,14 @@ Verify with `sudo nft list ruleset`.
 
 ## Git hooks
 
-Activated by `just init` via `git config core.hooksPath .githooks`:
+The user-level hooks at `~/.config/git/hooks/` (set as `core.hooksPath` in `dot_config/git/config`) apply globally and auto-dispatch into any repo's `<repo>/.githooks/<hookname>` if present — so projects can drop their own hooks at `.githooks/<name>` without ever touching `core.hooksPath` or writing passthrough stubs. Per-event behavior:
 
-- `pre-commit` → `just check`. Blocks commits that fail formatting or linting. Bypass with `git commit --no-verify`.
-- `post-commit` → `chezmoi apply`. Keeps `$HOME` in sync whenever a tracked file changes in the repo.
+- `pre-commit` → repo's `.githooks/pre-commit` (if any). No global logic. In this repo: `just check`.
+- `commit-msg` → repo's `.githooks/commit-msg` (if any), then strips any `Co-authored-by:` whose identity matches an AI agent (Copilot/Claude/Codex/…) so they don't trip the push gate.
+- `pre-push` → repo's `.githooks/pre-push` (if any), then rejects pushes that contain unsigned commits, commits with a foreign committer, or commits authored/co-authored by an AI agent.
+- `post-commit` → repo's `.githooks/post-commit` (if any). No global logic. In this repo: `chezmoi apply`.
+
+Bypass any of these with `--no-verify` on `commit`/`push`.
 
 ## Disaster recovery