feat: Hermit 1.1.0 — HERMIT_* env, Tauri desktop shell

Wire hermit_getenv across the engine, rebrand WebUI/systemd/docs, and
add apps/desktop (Tauri 2 + React) with a DeepSeek-Harness-like UI.
Qt app/ is frozen; full libcstcore FFI is scaffolded behind --features engine.

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

docs/desktop.md

@@ -0,0 +1,20 @@
+# Hermit Desktop (Tauri)
+
+Canonical GUI: [`apps/desktop`](../apps/desktop/). Qt under [`app/`](../app/) is frozen ([DEPRECATED](../app/DEPRECATED.md)).
+
+## Shape
+
+- **Shell**: Tauri 2 (Linux / Windows / macOS)
+- **UI**: React 19 — session rail, chat, tool cards, composer (DeepSeek Harness–like IA)
+- **Engine**: in-process `libcstcore` via Rust FFI (feature `engine`); without it the host uses a mock / echo path so the UI is developable
+
+## Dev
+
+```bash
+nix-shell -p rustc cargo nodejs_22 pkg-config webkitgtk_4_1 gtk3 librsvg openssl curl
+cd apps/desktop && npm install && npm run tauri dev
+```
+
+## Product env
+
+`HERMIT_*` preferred, `CST_*` accepted (see `hermit_getenv`). Config dir `~/.config/hermit`.