v1.1.2: action button, responsive faders, label scaling

Third integration-feedback release from building the streaming studio.

- New `Button` — a click-to-fire command button in the panel style, the
  non-latching sibling of PushButton. Implemented as PushButton's new
  `mode="action"` (never latches, press-down + brief LED flash, `onClick`);
  led="dot" (default) matches the corner-dot look, led={false} is plain.
- `fill` on LEDFader (parity with Fader) — faders stretch to fill their
  container in resizable panels instead of a fixed pixel length.
- `labelSize` on IndicatorLamp (and LampRow) — shrink the caption below its
  10px floor to match dense header rows.
- Docs: a dedicated "Buttons & switches" section with a decision guide
  (Button/PushButton/TransportButton/ToggleSwitch/SegmentSwitch) + live demos.

Library + docs typecheck and build; 38 tests pass.

apps/docs/src/App.tsx

@@ -1,6 +1,7 @@
 import React from 'react';
 import { AdvancedGuide } from './sections/AdvancedGuide';
 import { ApiDocs } from './sections/ApiDocs';
+import { Buttons } from './sections/Buttons';
 import { Console } from './sections/Console';
 import { Gallery } from './sections/Gallery';
 import { GettingStarted } from './sections/GettingStarted';
@@ -26,6 +27,7 @@ export const App: React.FC = () => (
         <div className="nav-links">
           <a href="#start">Start</a>
           <a href="#gallery">Gallery</a>
+          <a href="#buttons">Buttons</a>
           <a href="#synth">Synth</a>
           <a href="#playground">Playground</a>
           <a href="#guide">Guide</a>
@@ -36,6 +38,7 @@ export const App: React.FC = () => (
     <Hero />
     <GettingStarted />
     <Gallery />
+    <Buttons />
     <Console />
     <Synth />
     <Playground />