deprecate: make the idalib worker the default backend; mark mcp path for removal

Opening a binary now defaults to our own idalib worker; the ida-pro-mcp HTTP
supervisor path is deprecated (kept only for --db/attach and --backend mcp).

* launch.py: --backend default resolves to worker for a fresh binary open, mcp
  for the attach modes (--db / bare `ida-tui`, which have no worker equivalent);
  explicit --backend or IDATUI_BACKEND still wins. Logs a deprecation notice when
  the mcp path is used.
* Deprecation markers on client.py and server/patch_server.py; the ida-tui shell
  header and README now describe the worker as primary and note
  $IDATUI_WORKER_PYTHON. TODO tracks the removal checklist.

No code deleted yet — the mcp fallback stays until the worker is proven on a box
where idalib can spawn (pilot against --backend worker is the gate). Backend
resolution matrix verified: `ida-tui bash`->worker, bare/`--db`->mcp, explicit
flag/env honored.

2 files changed, 21 insertions, 4 deletions

diff --git a/idatui/client.py b/idatui/client.py
index 3e5edb4..f39a10d 100644
--- a/idatui/client.py
+++ b/idatui/client.py
@@ -1,5 +1,12 @@
 """Persistent, thread-safe client for the ida-pro-mcp (idalib) MCP server.
 
+DEPRECATED. The default backend is now our own idalib worker (idatui.worker +
+idatui.worker_client.WorkerClient), which talks a unix socket instead of HTTP and
+is ~50-100x cheaper per call. This module (and the whole ida-pro-mcp
+supervisor/HTTP path: server/patch_server.py, spawn.sh, launch.py's server
+plumbing) is kept only for `--backend mcp` / --db attach and will be removed once
+the worker is battle-tested. Prefer WorkerClient for new code.
+
 This is the foundation the whole TUI stands on. Unlike the throwaway CLI in the
 ida-mcp skill (which re-does the MCP handshake and spins a fresh socket on every
 call), this client:
diff --git a/idatui/launch.py b/idatui/launch.py
index 15352d5..b2f0eec 100644
--- a/idatui/launch.py
+++ b/idatui/launch.py
@@ -189,12 +189,22 @@ def main(argv: list[str] | None = None) -> int:
                    help="listen for RPC on this unix socket (puppeteer the TUI)")
     p.add_argument("--no-server", action="store_true",
                    help="do not auto-start the supervisor if it's down")
-    p.add_argument("--backend", choices=("mcp", "worker"),
-                   default=os.environ.get("IDATUI_BACKEND", "mcp"),
-                   help="'mcp' (ida-pro-mcp supervisor, default) or 'worker' "
-                        "(our own in-process idalib worker over a unix socket)")
+    p.add_argument("--backend", choices=("mcp", "worker"), default=None,
+                   help="'worker' (our own idalib worker over a unix socket, the "
+                        "default when opening a binary) or 'mcp' (deprecated "
+                        "ida-pro-mcp supervisor; used for --db/attach)")
     args = p.parse_args(argv)
 
+    # Backend selection: explicit flag > IDATUI_BACKEND > worker for a fresh
+    # binary open, mcp for the attach modes (--db / bare `ida-tui`) which have no
+    # worker equivalent. The mcp path is deprecated and on its way out.
+    if args.backend is None:
+        args.backend = os.environ.get("IDATUI_BACKEND") or (
+            "worker" if (args.binary and not args.db) else "mcp")
+    if args.backend == "mcp":
+        _log("using the deprecated ida-pro-mcp backend "
+             "(the idalib worker is default for opening a binary)")
+
     binary = None
     if args.binary and not args.db:
         binary = os.path.abspath(os.path.expanduser(args.binary))