fix(packaging): ship bundled skills in wheel

Salvages #23738 by @LeonSGP43. Wheel installs were missing skills/ and
optional-skills/ because pyproject's [tool.setuptools.packages.find]
only includes Python packages — the skills directories don't have
__init__.py so they were silently dropped from the wheel.

Adds setup.py with data_files spec emitting skills/* and optional-skills/*
under hermes_agent-<v>.data/data/, and a get_bundled_skills_dir() helper
in hermes_constants that discovers the wheel-installed location via
sysconfig before falling back to a source-checkout path. tools/skills_sync
uses the helper so 'hermes update' works for pip-installed users.

setup.py

@@ -0,0 +1,28 @@
+from __future__ import annotations
+
+from collections import defaultdict
+from pathlib import Path
+
+from setuptools import setup
+
+
+REPO_ROOT = Path(__file__).parent.resolve()
+
+
+def _data_file_tree(root_name: str) -> list[tuple[str, list[str]]]:
+    root = REPO_ROOT / root_name
+    grouped: defaultdict[str, list[str]] = defaultdict(list)
+    for path in sorted(root.rglob("*")):
+        if not path.is_file():
+            continue
+        rel_path = path.relative_to(REPO_ROOT)
+        grouped[str(rel_path.parent)].append(str(rel_path))
+    return sorted(grouped.items())
+
+
+setup(
+    data_files=[
+        *_data_file_tree("skills"),
+        *_data_file_tree("optional-skills"),
+    ]
+)