Fix critical WebSocket origin bypass, zombie processes, and review findings

Addresses findings from Devin and Codex reviews on the merged PR #10:

- CRITICAL: /ws/terminal accepted connections from any origin - Starlette's
  CORSMiddleware does not protect WebSocket handshakes, so any webpage could
  open a socket to the dashboard's terminal and get an interactive shell on
  the user's machine. Now validates the Origin header against the same
  allowed-origins list used for CORS before accepting.
- PtySession.close() sent SIGKILL to the shell's PID but never reaped it via
  os.waitpid(), leaking a zombie process per closed terminal session.
- hermes_available() ran a real subprocess (possibly bridged through WSL) on
  every /api/status poll, which the dashboard hits every 15s. Added a 60s
  TTL cache.
- create_skill() now also creates learnings.md and the context/ directory,
  matching the standard skill template (_template/) instead of only
  writing SKILL.md.
- The '+ New Skill' button stayed visible in the Skills Hub detail view
  since only its sibling filter input was hidden; both now live under a
  shared #skillActions container that's hidden/shown together.

Verified: malicious/missing-origin WebSocket connections are rejected at
the handshake (HTTP 403) before any shell spawns; a valid dashboard origin
still connects and works; closing a session leaves no zombie/orphaned
process; the hermes availability cache avoids repeat subprocess spawns.

dashboard/pages/skills.js

@@ -6,7 +6,7 @@ async function renderSkills() {
         <h1 class="page-title">Skills Hub</h1>
         <p class="page-subtitle">Browse, run, and monitor skill performance</p>
       </div>
-      <div class="btn-group">
+      <div class="btn-group" id="skillActions">
         <input id="skillFilter" class="form-input" style="width:200px" placeholder="Filter skills..." oninput="filterSkills()">
         <button class="btn btn-primary" onclick="showAddSkill()">+ New Skill</button>
       </div>
@@ -83,7 +83,7 @@ function filterSkills() {
 async function showSkillDetail(name) {
   document.getElementById('skillsContainer').style.display = 'none';
   document.getElementById('skillTabs').style.display = 'none';
-  document.getElementById('skillFilter').style.display = 'none';
+  document.getElementById('skillActions').style.display = 'none';
   const detail = document.getElementById('skillDetail');
   detail.style.display = 'block';
   detail.innerHTML = `<div class="loading"><div class="loading-spinner"></div></div>`;
@@ -152,7 +152,7 @@ async function showSkillDetail(name) {
 function backToSkills() {
   document.getElementById('skillsContainer').style.display = '';
   document.getElementById('skillTabs').style.display = '';
-  document.getElementById('skillFilter').style.display = '';
+  document.getElementById('skillActions').style.display = '';
   document.getElementById('skillDetail').style.display = 'none';
 }
 

server.py

@@ -166,12 +166,22 @@ def hermes_cli_args(*args: str) -> list:
         return ["wsl", "-e", "bash", "-lc", f"hermes {quoted}"]
     return ["hermes", *args]
 
+_hermes_available_cache = {"checked_at": 0.0, "result": False}
+HERMES_AVAILABLE_CACHE_TTL = 60
+
 def hermes_available() -> bool:
+    """Cached: this spawns a subprocess (possibly via WSL), and /api/status is polled every 15s."""
+    now = time.time()
+    if now - _hermes_available_cache["checked_at"] < HERMES_AVAILABLE_CACHE_TTL:
+        return _hermes_available_cache["result"]
     try:
         r = subprocess.run(hermes_cli_args("--version"), capture_output=True, text=True, timeout=10)
-        return r.returncode == 0
+        result = r.returncode == 0
     except Exception:
-        return False
+        result = False
+    _hermes_available_cache["checked_at"] = now
+    _hermes_available_cache["result"] = result
+    return result
 
 def check_agent(name: str) -> dict:
     """Filesystem-based check for opencode/gemini; hermes needs a real subprocess since it may live inside WSL."""
@@ -300,7 +310,9 @@ def create_skill(data: SkillCreate):
     if path.exists():
         raise HTTPException(409, "Skill already exists")
     path.mkdir(parents=True)
+    (path / "context").mkdir()
     (path / "SKILL.md").write_text(data.skill_md, encoding="utf-8")
+    (path / "learnings.md").write_text("", encoding="utf-8")
     append_audit({"action": "skill_created", "skill": data.name})
     return {"name": data.name}
 
@@ -838,9 +850,20 @@ class PtySession:
                     os.kill(self.pid, signal.SIGKILL)
                 except OSError:
                     pass
+                try:
+                    os.waitpid(self.pid, 0)  # reap the killed child so it doesn't stay a zombie
+                except ChildProcessError:
+                    pass
 
 @app.websocket("/ws/terminal")
 async def ws_terminal(websocket: WebSocket):
+    # CORSMiddleware does not protect WebSocket handshakes, so this endpoint - which spawns a
+    # full interactive shell - must check the Origin header itself, or any webpage could open
+    # this socket and get command execution on the machine running the dashboard.
+    origin = websocket.headers.get("origin")
+    if origin not in get_cors_origins():
+        await websocket.close(code=1008)
+        return
     await websocket.accept()
     session = PtySession()
     try: