chore(#2185): add scripts/pre-push hook to catch lint failures before CI

Wraps check-issue-refs.sh and check-comment-blocks.sh so a push that
would fail the tracker-tag or comment-block CI jobs is caught locally
before it reaches the remote — eliminating the fix-and-repush round-trip.

Install once per clone:
  ln -sf ../../scripts/pre-push .git/hooks/pre-push

Also adds a one-liner hint to CLAUDE.md so it surfaces in every
agent's context at session start.

CLAUDE.md

@@ -129,3 +129,6 @@ The docs below own the details — this section just points at them.
   window:** → [`docs/turn-loop.md`](docs/turn-loop.md).
 - **Two-step spawn, approval flow, flake.lock validation:** →
   [`docs/approvals.md`](docs/approvals.md).
+- **Pre-push lint hook** (catches tracker-tag and comment-block failures
+  before CI does — install once per clone):
+  `ln -sf ../../scripts/pre-push .git/hooks/pre-push`

scripts/pre-push

@@ -0,0 +1,32 @@
+#!/bin/sh
+# Git pre-push hook: runs the tracker-tag lint and the comment-block
+# lint against the working tree before any push lands on the remote.
+# Catches issues that would fail CI and require a follow-up commit
+# (common failure mode: a nix comment containing a hash-issue-number
+# tag added mid-session).
+#
+# Install (once per clone):
+#   ln -sf ../../scripts/pre-push .git/hooks/pre-push
+#
+# The hook runs against the full working tree (not just staged or
+# pushed files) to match what CI sees: `nix flake check` builds from
+# the committed tree, so an untracked hit on a staged file would still
+# trip CI.
+set -eu
+
+repo_root="$(git rev-parse --show-toplevel)"
+
+echo "pre-push: running tracker-tag lint..." >&2
+if ! sh "$repo_root/scripts/check-issue-refs.sh"; then
+  echo "pre-push: tracker-tag lint FAILED — fix before pushing" >&2
+  exit 1
+fi
+
+echo "pre-push: running comment-block lint..." >&2
+if ! sh "$repo_root/scripts/check-comment-blocks.sh"; then
+  echo "pre-push: comment-block lint FAILED — fix before pushing" >&2
+  exit 1
+fi
+
+echo "pre-push: lints passed ✓" >&2
+exit 0