feat: session delete + touch-friendly message controls

Session delete:
- DELETE /sessions/{session_id} endpoint (chat.py + session_store.py)
- × button on each session item in the panel (hover-reveal on desktop)
- Clears UI if the active session is deleted

Touch accessibility:
- @media (hover: none) rule makes msg-actions always visible on touch devices
- msg-act-btn tap targets enlarged to 36px min-height, readable font size
- session-delete-btn also always visible and finger-sized on touch

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

cortex/routers/chat.py

@@ -6,7 +6,7 @@ from pydantic import BaseModel
 from context_loader import load_context
 from llm_client import complete
 from session_logger import log_turn
-from session_store import load as load_session, save as save_session, list_all, generate_session_id
+from session_store import load as load_session, save as save_session, list_all, generate_session_id, delete as delete_session
 from config import settings
 import event_bus
 
@@ -143,6 +143,14 @@ async def list_sessions() -> dict:
     return {"sessions": list_all()}
 
 
+@router.delete("/sessions/{session_id}")
+async def delete_session_endpoint(session_id: str) -> dict:
+    found = delete_session(session_id)
+    if not found:
+        raise HTTPException(status_code=404, detail=f"Session {session_id} not found")
+    return {"ok": True, "session_id": session_id}
+
+
 @router.put("/history/{session_id}")
 async def replace_history(session_id: str, req: HistoryUpdate) -> dict:
     """Replace the full message list for a session (used by edit/delete UI)."""

cortex/session_store.py

@@ -69,6 +69,15 @@ def save(session_id: str, messages: list[dict]) -> None:
     }, indent=2))
 
 
+def delete(session_id: str) -> bool:
+    """Delete a session file. Returns True if it existed and was deleted."""
+    path = _path(session_id)
+    if not path.exists():
+        return False
+    path.unlink()
+    return True
+
+
 def list_all() -> list[dict]:
     d = settings.sessions_path()
     if not d.exists():

cortex/static/app.js

@@ -183,6 +183,27 @@
                     `${s.message_count} msgs · ${timeAgo(s.updated)}`
                 );
                 item.addEventListener('click', () => resumeSession(s.session_id));
+
+                const delBtn = document.createElement('button');
+                delBtn.className = 'session-delete-btn';
+                delBtn.textContent = '×';
+                delBtn.title = 'Delete session';
+                delBtn.addEventListener('click', async (e) => {
+                    e.stopPropagation();
+                    await fetch(`/sessions/${s.session_id}`, { method: 'DELETE' });
+                    if (sessionId === s.session_id) {
+                        sessionId = null;
+                        currentHistory = [];
+                        messagesEl.innerHTML = '';
+                        sessionEl.textContent = '';
+                        addMessage('system', 'Session deleted');
+                    }
+                    const res = await fetch('/sessions');
+                    const data = await res.json();
+                    renderPanel(data.sessions);
+                });
+                item.appendChild(delBtn);
+
                 sessionsPanel.appendChild(item);
             }
         }

cortex/static/style.css

@@ -176,6 +176,23 @@
         .session-item:hover { background: var(--bg); }
         .session-item.new { color: var(--accent); justify-content: center; }
 
+        .session-delete-btn {
+            background: none;
+            border: none;
+            color: var(--muted);
+            font-size: 1.1rem;
+            line-height: 1;
+            padding: 2px 4px;
+            cursor: pointer;
+            border-radius: 3px;
+            flex-shrink: 0;
+            margin-left: 4px;
+            opacity: 0;
+            transition: opacity 0.15s, color 0.15s;
+        }
+        .session-item:hover .session-delete-btn { opacity: 1; }
+        .session-delete-btn:hover { color: #e06c75; }
+
         .session-id {
             font-family: monospace;
             font-size: 0.85rem;
@@ -1029,6 +1046,29 @@
             #note-type-btn { padding: 6px 10px; }
         }
 
+        /* ── Touch devices — no hover capability ─────────────────── */
+        /* Always show message controls; make tap targets finger-sized */
+        @media (hover: none) {
+            .msg-actions {
+                opacity: 1;
+                padding: 4px 2px 2px;
+            }
+
+            .msg-act-btn {
+                font-size: 0.78rem;
+                padding: 6px 12px;
+                min-height: 36px;
+            }
+
+            .session-delete-btn {
+                opacity: 1;
+                font-size: 1.3rem;
+                padding: 4px 8px;
+                min-width: 36px;
+                min-height: 36px;
+            }
+        }
+
         @media (max-width: 380px) {
             header .name { font-size: 1rem; }
             .header-emoji { font-size: 1.3rem; }