docs: README as overview + options, one docs page per feature

README keeps intro, feature list linking docs/, install, two sessions,
usage, the complete options table, changes outside Nix, rollback,
uninstall. Each feature's details (problem, what you get, configuration,
limitations, how it works) move to its own page in docs/; docs/dashboard.md
is split per feature and docs/changes-outside-nix.md becomes
docs/cleanup.md.

docs/window-control-bar.md

@@ -0,0 +1,57 @@
+# Window control bar
+
+`dashboard.frameControls.*`, module `frame-controls` ([options](../README.md#options)).
+
+A [SteamVR dashboard patch](ui-patches.md#steamvr-dashboard-patches).
+
+## Problem
+
+The controls under a dashboard window are fixed: some in the bottom bar,
+others only in the three-dot menu (curvature, dock to a controller), and
+theater windows have no "Float".
+
+## What you get
+
+- **long press** a bar icon or menu row (`longPressMs`; a progress ring
+  shows from half the time, at most after 1 s), then **Show in bar** in the
+  popup moves that control between bar and menu **for all windows**.
+  Placements survive SteamVR restarts and reboots (saved in
+  `~/.local/state/steam-frame-nix/ui-patches/frame-controls.json`, see
+  [Changes outside Nix](../README.md#changes-outside-nix-exceptions)).
+  Short presses stay stock.
+- `inBar` / `inMenu` set where controls start; a popup choice wins until
+  that control's entry changes.
+- `floatInTheater` gives theater windows the "Float" control.
+
+With [window curvature](window-curvature.md), a drag on the curvature
+control adjusts curvature and cancels the long press, also after the ring
+shows; once the ring shows, the drag needs 3× the usual travel
+(`dragThresholdPixels`, counted from where the press started), so laser
+drift during the hold doesn't cancel it.
+
+## Configuration
+
+```nix
+steamFrame.dashboard.frameControls = {
+  enable = true;
+  # longPressMs = 1500;
+  # inBar = [ "curvature" ];  inMenu = [ "theater" ];
+  # floatInTheater = true;
+};
+```
+
+## Limitations
+
+- Laser only: no right-click or thumbstick click reaches the dashboard;
+  gamepad navigation sees stock controls.
+- Placements are per control type, not per window.
+- The three-dot button itself can't be moved.
+
+## How it works
+
+`frame-controls`, with [persistent state](ui-patches.md#persistent-state)
+(placements). Works with window curvature through its
+[contract](window-curvature.md#contract-for-other-patches).
+
+Debugging: `window.__sfuiFrameControls.dump()`, `.placement()`, `.reset()`
+(forget choices), `.log`, `window.__sfuiFrameControlsState`.