feat: SSH dev routing, model registry UX, chat input toolbar, doc sync

Backend / infrastructure:
- cortex/tools/_projects.py (new): shared project alias registry with ssh_host
  for workstation projects (aether_api, aether_frontend, aether_container)
- cortex/tools/git.py: all git tools route to workstation via SSH when ssh_host set
- cortex/tools/aider.py: aider_run SSH-routes to workstation using bash -l -c
- cortex/routers/local_llm.py: POST /api/models/{id}/edit AJAX endpoint — save
  model edits without page reload or tab reset; returns JSON {ok, label, model_name}
- cortex/llm_client.py: remove Gemini CLI and Claude CLI backends; clean up
  fallback chain and process group tracking (continuation of Gemini CLI removal)
- cortex/routers/auth.py: strip Claude/Gemini CLI auth status checks (CLI removed)
- cortex/routers/chat.py: remove legacy claude/gemini backend fields
- cortex/config.py: clean up CLI-related settings
- cortex/main.py: remove CLI lifecycle hooks

UI:
- cortex/static/local_llm.html: model edit forms now save via fetch() + toast;
  stay on Models tab; update row header label in place on success
- cortex/static/index.html: restructure input area to column layout — textarea
  above, compact toolbar below (Chat/Tools/Attach + Send); fixes dead space at
  M/L/XL sizes; context panel "Role" → "Model" section label
- cortex/static/style.css: column input-area layout; #input-toolbar; flex:1 →
  width:100% on textarea (fixes scrollHeight in column flex context); compact
  send/stop button padding
- cortex/static/app.js: add XL (720px) to height cycle; default M (240px)

Docs:
- cortex/static/HELP.md: S/M/L → S/M/L/XL; add Rebuild to distill table; fix
  "Role selector" references (no such UI); fix "your active role" → Chat role;
  fix ⚡ toggle description; Model Registry section cleanup
- documentation/ARCH__BACKENDS.md: reflect CLI removal, current backend state

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

cortex/routers/chat.py

@@ -21,11 +21,7 @@ router = APIRouter()
 
 
 def _backend_label(backend: str, username: str, role: str = "chat") -> str:
-    """Human-readable label for the model that handled a request (legacy path)."""
-    if backend == "claude":
-        return "Claude"
-    if backend == "gemini":
-        return "Gemini"
+    """Human-readable label for the model that handled a request."""
     if backend == "local":
         cfg = model_registry.get_best_local_model(username, role)
         if cfg:
@@ -52,7 +48,7 @@ class ChatRequest(BaseModel):
     message: str
     session_id: str | None = None
     tier: int | None = None
-    model: str | None = None        # legacy backend override ("claude"|"gemini"|"local")
+    model: str | None = None        # ignored — kept for API compatibility
     slot: str | None = None         # Phase 3: explicit slot ("primary"|"backup_1"|"backup_2")
     chat_role: str = "chat"         # active role: "chat"|"coder"|"research"|"distill" etc.
     include_long: bool = True
@@ -64,10 +60,6 @@ class ChatRequest(BaseModel):
     attachment: Attachment | None = None  # image attachment (text files injected client-side)
 
 
-class BackendRequest(BaseModel):
-    primary: str  # "claude", "gemini", or "local"
-
-
 class NoteRequest(BaseModel):
     session_id: str
     note: str
@@ -183,9 +175,6 @@ async def _stream_chat(req: ChatRequest):
             yield f"data: {json.dumps({'type': 'error', 'message': str(e)})}\n\n"
 
     finally:
-        # Ensure the LLM task is cancelled if the generator is torn down
-        # (e.g. client disconnect or server shutdown). This propagates
-        # CancelledError into _gemini() which kills the process group.
         if not task.done():
             task.cancel()
             try:
@@ -203,10 +192,6 @@ async def chat(req: ChatRequest) -> StreamingResponse:
     )
 
 
-_BACKEND_CYCLE = ("claude", "gemini", "local")
-_BACKEND_FALLBACK = {"claude": "gemini", "gemini": "claude", "local": "claude"}
-
-
 def _request_user(request: Request) -> str | None:
     """Extract username from JWT cookie, or None."""
     try:
@@ -216,20 +201,6 @@ def _request_user(request: Request) -> str | None:
         return None
 
 
-def _local_model_info(request: Request) -> dict | None:
-    """Return the best local model {label, model_name} for the session user, or None."""
-    username = _request_user(request)
-    if not username:
-        return None
-    try:
-        cfg = model_registry.get_best_local_model(username, "chat")
-        if cfg:
-            return {"label": cfg.get("label", ""), "model_name": cfg.get("model_name", "")}
-    except Exception:
-        pass
-    return None
-
-
 def _chat_slot_models(username: str) -> list[dict]:
     """Return [{slot, label, type}] for each configured slot in the chat role, primary first."""
     registry = model_registry.get_registry(username)
@@ -279,7 +250,6 @@ async def get_backend(request: Request) -> dict:
     username        = _request_user(request)
     chat_models     = _chat_slot_models(username) if username else []
     available_roles = _available_roles_for_toggle(username) if username else []
-    p = settings.primary_backend
 
     orch_label = None
     if username:
@@ -288,25 +258,9 @@ async def get_backend(request: Request) -> dict:
             orch_label = orch_cfg.get("label") or orch_cfg.get("model_name") or None
 
     return {
-        "chat_models":        chat_models,       # Phase 3: [{slot, label, type}] for chat-role slots
-        "available_roles":    available_roles,    # kept for banner + backward compat
+        "chat_models":        chat_models,
+        "available_roles":    available_roles,
         "orchestrator_model": orch_label,
-        # Legacy fields kept for backward compat
-        "primary":     p,
-        "fallback":    _BACKEND_FALLBACK.get(p, "claude"),
-        "local_model": _local_model_info(request),
-    }
-
-
-@router.post("/backend")
-async def set_backend(req: BackendRequest, request: Request) -> dict:
-    if req.primary not in _BACKEND_CYCLE:
-        raise HTTPException(status_code=400, detail="primary must be 'claude', 'gemini', or 'local'")
-    settings.primary_backend = req.primary
-    return {
-        "primary":     req.primary,
-        "fallback":    _BACKEND_FALLBACK[req.primary],
-        "local_model": _local_model_info(request),
     }