refactor: archive GUI clients; keep minimal TUI with hooks/API

Move Qt/Tauri/full Web SPA under archive/, ship hermit as CLI/TUI plus
libcstcore and cst-webui/1 HTTP+SSE (turn lifecycle hooks, capabilities).

Co-authored-by: Cursor <cursoragent@cursor.com>

archive/qt-app/DEPRECATED.md

@@ -0,0 +1,10 @@
+# Deprecated: Qt front end (archived)
+
+This directory is the **legacy Qt 6 / QML** Hermit GUI (`cst-agent-app`),
+formerly at `app/`. It is **frozen** under `archive/qt-app`.
+
+Hermit’s product surface is the CLI/TUI + `libcstcore` + `--web` (`cst-webui/1`).
+Another archived desktop shell is `archive/desktop-tauri` (Tauri 2 + React).
+
+Do not add features here. Experimental rebuild: `-DCST_BUILD_APP=ON` from the
+repo root (see root `archive/README.md`).