hooks: refuse master, cap a code commit at 300 lines, require the task ref (V-445)

Two git hooks, tracked in .githooks and wired with core.hooksPath so a
fresh clone gets them with one config line.

pre-commit refuses master and refuses more than 300 changed lines in
non-markdown files. Markdown is exempt because docs land as one batch.
This is a commit-time guard, which diff-budget.sh is not: that hook
blocks the agent's edits and says nothing when either of us commits.

commit-msg requires (V-<id>), not (#<id>). Gitea autolinks # to its own
issues, and Vikunja is the tracker.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

.githooks/commit-msg

@@ -0,0 +1,30 @@
+#!/bin/sh
+# Every commit names the Vikunja task it belongs to.
+#
+#   router: narrow the single-token rule (V-359)
+#
+# V- and not #, because Gitea autolinks #359 to a Gitea issue, which is a
+# different tracker and a wrong link.
+#
+# Exempt: merges, reverts, fixup/squash, and the initial commit.
+
+msg_file=$1
+subject=$(sed -n '1p' "$msg_file")
+
+case "$subject" in
+	Merge\ *|Revert\ *|fixup!\ *|squash!\ *|amend!\ *) exit 0 ;;
+esac
+
+if [ -f "$(git rev-parse --git-dir)/MERGE_HEAD" ]; then
+	exit 0
+fi
+
+if printf '%s' "$subject" | grep -qE '\(V-[0-9]+\)$'; then
+	exit 0
+fi
+
+echo "commit-msg: subject must end with a Vikunja task ref." >&2
+echo "  got:  $subject" >&2
+echo "  want: router: narrow the single-token rule (V-359)" >&2
+echo "  No task yet? Create one. Work without a task is work nobody can resume." >&2
+exit 1

.githooks/pre-commit

@@ -0,0 +1,30 @@
+#!/bin/sh
+# Two guards, both bypassable with --no-verify when you mean it.
+#   1. master is not a working branch.
+#   2. a code commit stays under 300 changed lines.
+# Markdown is exempt from the size cap on purpose: docs land as one batch.
+
+branch=$(git symbolic-ref --short HEAD 2>/dev/null)
+
+case "$branch" in
+	master|main)
+		echo "pre-commit: refusing to commit on $branch." >&2
+		echo "  task start <vikunja-id>   # branch off origin/master, write TASK.md" >&2
+		exit 1
+		;;
+esac
+
+# Added + deleted lines across staged files that are not markdown.
+# numstat prints "-\t-\t<path>" for binaries; those count 0 and that is fine,
+# a binary blob is not the kind of diff this cap exists to stop.
+loc=$(git diff --cached --numstat -- . ':(exclude)*.md' |
+	awk '$1 ~ /^[0-9]+$/ { a += $1 } $2 ~ /^[0-9]+$/ { d += $2 } END { print a + d + 0 }')
+
+if [ "$loc" -gt 300 ]; then
+	echo "pre-commit: $loc changed lines in non-markdown files, cap is 300." >&2
+	echo "  Split it. Each commit should be one reviewable idea." >&2
+	echo "  git reset <path> to unstage, or --no-verify if this genuinely cannot split." >&2
+	exit 1
+fi
+
+exit 0