fix(skills): exclude .archive from skill index walk

Archived skills (moved to ~/.hermes/skills/.archive/ by the curator)
were still surfaced in the <available_skills> system prompt under a
fake '.archive' category, causing the agent to load and try to use
deprecated skills. The os.walk in iter_skill_index_files() only
excluded .git/.github/.hub.

Add '.archive' to EXCLUDED_SKILL_DIRS, and to the two other places
that hardcode the same exclusion tuple (gateway/run.py and
agent/skill_commands.py).

agent/skill_utils.py

@@ -24,7 +24,7 @@ PLATFORM_MAP = {
     "windows": "win32",
 }
 
-EXCLUDED_SKILL_DIRS = frozenset((".git", ".github", ".hub"))
+EXCLUDED_SKILL_DIRS = frozenset((".git", ".github", ".hub", ".archive"))
 
 # ── Lazy YAML loader ─────────────────────────────────────────────────────
 
@@ -440,7 +440,7 @@ def extract_skill_description(frontmatter: Dict[str, Any]) -> str:
 def iter_skill_index_files(skills_dir: Path, filename: str):
     """Walk skills_dir yielding sorted paths matching *filename*.
 
-    Excludes ``.git``, ``.github``, ``.hub`` directories.
+    Excludes ``.git``, ``.github``, ``.hub``, ``.archive`` directories.
     """
     matches = []
     for root, dirs, files in os.walk(skills_dir, followlinks=True):