feat(maestro-tui): wire --config flag + document tui in INSTALL.md (NAP-283)

- `RunConfig` grows a `config_path: Option<PathBuf>` field, plumbed from the
  umbrella binary's global `--config` flag through to `MaestroConfigFile`
  loading. Explicit `--config <path>` wins over `$MAESTRO_CONFIG` over the
  platform default; a missing file still falls back to shipped defaults.
- `docs/INSTALL.md` gains a "terminal UI" section: that `maestro tui` ships
  in the default feature set, how to opt out (`--no-default-features
  --features cli,daemon`), the `MAESTRO_DAEMON_URL` override, and a worked
  example of `[tui]` / `[tui.keymap.normal]` config pointing at the
  full action vocabulary in the design spec.
- Adds a thin-build line for `--features cli` (CLI-only client) and lists
  `tui` in the default-feature set.
- CLAUDE.md repo-layout block lists the new `maestro-tui` crate.

Closes the NAP-275 v1 epic.

docs/INSTALL.md

@@ -52,8 +52,8 @@ The binary lands in `~/.cargo/bin/maestro` — make sure that's on your `$PATH`.
 
 ## Thin builds for single-role hosts
 
-The default install pulls in everything. Registry-only and daemon-only hosts
-can opt out of unused dependencies:
+The default install pulls in everything (`cli` + `daemon` + `registry` + `tui`).
+Single-role hosts can opt out of unused dependencies:
 
 ```sh
 # Registry server — no tmux/PTY/jwt-verifier code:
@@ -63,10 +63,52 @@ cargo install --git https://git.naps.pt/naps62/maestro \
 # Daemon-only host — no embedded web assets, no registry HTTP surface:
 cargo install --git https://git.naps.pt/naps62/maestro \
   --no-default-features --features daemon --locked maestro
+
+# CLI-only client (no local daemon, no TUI):
+cargo install --git https://git.naps.pt/naps62/maestro \
+  --no-default-features --features cli --locked maestro
 ```
 
 The wizard always installs the default-feature build.
 
+## The terminal UI: `maestro tui`
+
+`maestro tui` is the keyboard-and-mouse driven terminal UI client. It ships
+in the default feature set, so a vanilla `cargo install maestro` builds it.
+Drop the `tui` feature to skip it on hosts that don't need the UI surface
+(`--no-default-features --features cli,daemon`).
+
+It talks only to the **local** `maestro daemon` over `http://127.0.0.1:7070`
+by default; peer daemons reach you transparently via the catalog mirror.
+Override the daemon URL with `--daemon-url` or `$MAESTRO_DAEMON_URL`.
+
+The `[tui]` section in `~/.config/maestro/config.toml` (or whatever path you
+pass via the global `--config` flag) controls the keymap. Shipped defaults
+cover every v1 action — only override what you want to change:
+
+```toml
+[tui]
+leader = "ctrl-a"            # one byte that escapes Insert mode
+chord_timeout_ms = 1000      # how long to hold a partial chord like `g`
+
+[tui.keymap.normal]
+"i"            = "EnterInsert"
+"s"            = "OpenSpawnModal"
+"x"            = "KillHighlighted"
+"?"            = "ShowHelp"
+"ctrl-t"       = "NewTab"
+"g t"          = "NextTab"
+"ctrl-w h"     = "FocusSidebar"
+"enter"        = "AttachHighlighted"
+
+[tui.keymap.insert]
+# (leader is added automatically as LeaveInsert; only override here when you
+# want extra Insert-mode bindings)
+```
+
+The full action vocabulary lives in
+`docs/superpowers/specs/2026-05-28-maestro-tui-design.md` §3.8.
+
 ## Adding the browser UI (optional)
 
 `maestro-web` is a separate binary that serves the SPA bundle and reverse-