Add automatic patch-version bumping via a tracked git pre-commit hook

pyproject.toml's version has never moved past the 1.0.0 scaffold value
across 368 commits; there was no bump mechanism at all, Claude-driven or
otherwise. Add .githooks/pre-commit (stdlib Python, no dependencies) that
increments the patch version on every commit and stages it automatically,
deferring to a deliberate version edit already staged in the same commit
and skipping merge commits. Wire it in via `make install` (git config
core.hooksPath .githooks) so it activates for every clone without
requiring any change to existing workflows.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TwLhnueWrsK15wrieXE5m7

.githooks/pre-commit

@@ -0,0 +1,51 @@
+#!/usr/bin/env python3
+# retoor <retoor@molodetz.nl>
+
+import re
+import subprocess
+import sys
+from pathlib import Path
+
+REPO_ROOT = Path(
+    subprocess.run(
+        ["git", "rev-parse", "--show-toplevel"],
+        capture_output=True,
+        text=True,
+        check=True,
+    ).stdout.strip()
+)
+PYPROJECT = REPO_ROOT / "pyproject.toml"
+VERSION_LINE = re.compile(r'^version = "(\d+)\.(\d+)\.(\d+)"$', re.MULTILINE)
+STAGED_VERSION_CHANGE = re.compile(r'^[+-]version = "\d+\.\d+\.\d+"$', re.MULTILINE)
+
+
+def staged_diff(path: Path) -> str:
+    result = subprocess.run(
+        ["git", "diff", "--cached", "--unified=0", "--", str(path)],
+        capture_output=True,
+        text=True,
+        cwd=REPO_ROOT,
+    )
+    return result.stdout
+
+
+def main() -> int:
+    if (REPO_ROOT / ".git" / "MERGE_HEAD").exists():
+        return 0
+    if not PYPROJECT.is_file():
+        return 0
+    if STAGED_VERSION_CHANGE.search(staged_diff(PYPROJECT)):
+        return 0
+    text = PYPROJECT.read_text()
+    match = VERSION_LINE.search(text)
+    if not match:
+        return 0
+    major, minor, patch = (int(part) for part in match.groups())
+    bumped = f'version = "{major}.{minor}.{patch + 1}"'
+    PYPROJECT.write_text(VERSION_LINE.sub(bumped, text, count=1))
+    subprocess.run(["git", "add", str(PYPROJECT)], cwd=REPO_ROOT, check=True)
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())