Add cache pinning and discard functionality

- Pin items when published (published, input_to_published)
- Discard endpoint (DELETE /cache/{hash}) refuses pinned items
- UI shows pin status and discard button on cache detail
- Run publish also pins output and all inputs for provenance

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

server.py

@@ -596,6 +596,8 @@ async def ui_cache_meta_form(content_hash: str, request: Request):
     tags = meta.get("tags", [])
     tags_str = ", ".join(tags) if tags else ""
     published = meta.get("published", {})
+    pinned = meta.get("pinned", False)
+    pin_reason = meta.get("pin_reason", "")
 
     # Detect media type for publish
     cache_path = CACHE_DIR / content_hash
@@ -706,6 +708,28 @@ async def ui_cache_meta_form(content_hash: str, request: Request):
         <h3 class="text-lg font-semibold text-white mb-4">Publish to L2 (ActivityPub)</h3>
         {publish_html}
     </div>
+
+    <!-- Status & Actions Section -->
+    <div class="border-t border-dark-500 pt-6 mt-6">
+        <h3 class="text-lg font-semibold text-white mb-4">Status</h3>
+        <div class="bg-dark-600 rounded-lg p-4 mb-4">
+            <div class="flex items-center gap-2 mb-2">
+                <span class="text-sm text-gray-400">Pinned:</span>
+                {'<span class="text-green-400">Yes</span>' if pinned else '<span class="text-gray-500">No</span>'}
+                {f'<span class="text-xs text-gray-500 ml-2">({pin_reason})</span>' if pinned and pin_reason else ''}
+            </div>
+            <p class="text-xs text-gray-500">Pinned items cannot be discarded. Items are pinned when published or used as inputs to published content.</p>
+        </div>
+
+        <div id="discard-result"></div>
+        {'<p class="text-gray-500 text-sm">Cannot discard pinned items.</p>' if pinned else f"""
+        <button hx-delete="/ui/cache/{content_hash}/discard" hx-target="#discard-result" hx-swap="innerHTML"
+                hx-confirm="Are you sure you want to discard this item? This cannot be undone."
+                class="px-4 py-2 bg-red-600 hover:bg-red-700 text-white font-medium rounded-lg transition-colors">
+            Discard Item
+        </button>
+        """}
+    </div>
     '''
 
 
@@ -826,7 +850,7 @@ async def ui_publish_cache(content_hash: str, request: Request):
         "published_at": datetime.now(timezone.utc).isoformat(),
         "last_synced_at": datetime.now(timezone.utc).isoformat()
     }
-    save_cache_meta(content_hash, published=publish_info)
+    save_cache_meta(content_hash, published=publish_info, pinned=True, pin_reason="published")
 
     return f'''
     <div class="bg-green-900/50 border border-green-700 text-green-300 px-4 py-3 rounded-lg mb-4">
@@ -904,6 +928,81 @@ async def list_cache():
     return [f.name for f in CACHE_DIR.iterdir() if f.is_file()]
 
 
+@app.delete("/cache/{content_hash}")
+async def discard_cache(content_hash: str, username: str = Depends(get_required_user)):
+    """
+    Discard (delete) a cached item.
+
+    Refuses to delete pinned items. Pinned items include:
+    - Published items
+    - Inputs to published items
+    """
+    cache_path = CACHE_DIR / content_hash
+    if not cache_path.exists():
+        raise HTTPException(404, "Content not found")
+
+    # Check ownership
+    user_hashes = get_user_cache_hashes(username)
+    if content_hash not in user_hashes:
+        raise HTTPException(403, "Access denied")
+
+    # Check if pinned
+    meta = load_cache_meta(content_hash)
+    if meta.get("pinned"):
+        pin_reason = meta.get("pin_reason", "unknown")
+        raise HTTPException(400, f"Cannot discard pinned item (reason: {pin_reason})")
+
+    # Delete the file and metadata
+    cache_path.unlink()
+    meta_path = CACHE_DIR / f"{content_hash}.meta.json"
+    if meta_path.exists():
+        meta_path.unlink()
+    # Also delete transcoded mp4 if exists
+    mp4_path = CACHE_DIR / f"{content_hash}.mp4"
+    if mp4_path.exists():
+        mp4_path.unlink()
+
+    return {"discarded": True, "content_hash": content_hash}
+
+
+@app.delete("/ui/cache/{content_hash}/discard", response_class=HTMLResponse)
+async def ui_discard_cache(content_hash: str, request: Request):
+    """HTMX handler: discard a cached item."""
+    current_user = get_user_from_cookie(request)
+    if not current_user:
+        return '<div class="bg-red-900/50 border border-red-700 text-red-300 px-4 py-3 rounded-lg mb-4">Login required</div>'
+
+    # Check ownership
+    user_hashes = get_user_cache_hashes(current_user)
+    if content_hash not in user_hashes:
+        return '<div class="bg-red-900/50 border border-red-700 text-red-300 px-4 py-3 rounded-lg mb-4">Access denied</div>'
+
+    cache_path = CACHE_DIR / content_hash
+    if not cache_path.exists():
+        return '<div class="bg-red-900/50 border border-red-700 text-red-300 px-4 py-3 rounded-lg mb-4">Content not found</div>'
+
+    # Check if pinned
+    meta = load_cache_meta(content_hash)
+    if meta.get("pinned"):
+        pin_reason = meta.get("pin_reason", "unknown")
+        return f'<div class="bg-red-900/50 border border-red-700 text-red-300 px-4 py-3 rounded-lg mb-4">Cannot discard: item is pinned ({pin_reason})</div>'
+
+    # Delete the file and metadata
+    cache_path.unlink()
+    meta_path = CACHE_DIR / f"{content_hash}.meta.json"
+    if meta_path.exists():
+        meta_path.unlink()
+    mp4_path = CACHE_DIR / f"{content_hash}.mp4"
+    if mp4_path.exists():
+        mp4_path.unlink()
+
+    return '''
+    <div class="bg-green-900/50 border border-green-700 text-green-300 px-4 py-3 rounded-lg mb-4">
+        Item discarded. <a href="/ui?tab=cache" class="underline">Back to cache</a>
+    </div>
+    '''
+
+
 # Known assets (bootstrap data)
 KNOWN_ASSETS = {
     "cat": "33268b6e167deaf018cc538de12dbe562612b33e89a749391cef855b320a269b",
@@ -1181,14 +1280,14 @@ async def publish_cache_to_l2(
     except Exception as e:
         raise HTTPException(500, f"L2 publish failed: {e}")
 
-    # Update local metadata with publish status
+    # Update local metadata with publish status and pin
     publish_info = {
         "to_l2": True,
         "asset_name": req.asset_name,
         "published_at": datetime.now(timezone.utc).isoformat(),
         "last_synced_at": datetime.now(timezone.utc).isoformat()
     }
-    save_cache_meta(content_hash, published=publish_info)
+    save_cache_meta(content_hash, published=publish_info, pinned=True, pin_reason="published")
 
     return {
         "published": True,
@@ -1665,6 +1764,11 @@ async def ui_publish_run(run_id: str, request: Request, output_name: str = Form(
     if not token:
         return HTMLResponse('<div class="error">Not logged in</div>')
 
+    # Get the run to pin its output and inputs
+    run = load_run(run_id)
+    if not run:
+        return HTMLResponse('<div class="bg-red-900/50 border border-red-700 text-red-300 px-4 py-3 rounded-lg">Run not found</div>')
+
     # Call L2 to publish the run, including this L1's public URL
     # Longer timeout because L2 calls back to L1 to fetch run details
     try:
@@ -1679,6 +1783,15 @@ async def ui_publish_run(run_id: str, request: Request, output_name: str = Form(
             return HTMLResponse(f'<div class="error">Error: {error}</div>')
         resp.raise_for_status()
         result = resp.json()
+
+        # Pin the output
+        if run.output_hash:
+            save_cache_meta(run.output_hash, pinned=True, pin_reason="published")
+
+        # Pin the inputs (for provenance)
+        for input_hash in run.inputs:
+            save_cache_meta(input_hash, pinned=True, pin_reason="input_to_published")
+
         return HTMLResponse(f'''
             <div class="bg-green-900/50 border border-green-700 text-green-300 px-4 py-3 rounded-lg mb-4">
                 Published to L2 as <strong>{result["asset"]["name"]}</strong>