fix(tui): Ctrl+C with input selection actually preserves input (lift handler to app level)

Previous fix in 9dbf1ec6 handled Ctrl+C inside textInput but the APP-level
useInputHandlers fires the same keypress in a separate React hook and ran
clearIn() regardless. Net effect: the OSC 52 copy succeeded but the input
wiped right after, so Brooklyn only noticed the wipe.

Lift the selection-aware Ctrl+C to a single place by threading input
selection state through a new nanostore (src/app/inputSelectionStore.ts).
textInput syncs its derived `selected` range + a clear() callback to the
store on every selection change, and the app-level Ctrl+C handler reads
the store before its clear/interrupt/die chain:

  - terminal-level selection (scrollback) → copy, existing behavior
  - in-input selection present → copy + clear selection, preserve input
  - input has text, no selection → clearIn(), existing behavior
  - empty + busy → interrupt turn
  - empty + idle → die

textInput no longer has its own Ctrl+C block; keypress falls through to
app-level like it did before 9dbf1ec6.

ui-tui/src/app/useInputHandlers.ts

@@ -8,6 +8,9 @@ import type {
   VoiceRecordResponse
 } from '../gatewayTypes.js'
 
+import { writeOsc52Clipboard } from '../lib/osc52.js'
+
+import { getInputSelection } from './inputSelectionStore.js'
 import type { InputHandlerContext, InputHandlerResult } from './interfaces.js'
 import { $isBlocked, $overlayState, patchOverlayState } from './overlayStore.js'
 import { turnController } from './turnController.js'
@@ -247,6 +250,15 @@ export function useInputHandlers(ctx: InputHandlerContext): InputHandlerResult {
         return copySelection()
       }
 
+      const inputSel = getInputSelection()
+
+      if (inputSel && inputSel.end > inputSel.start) {
+        writeOsc52Clipboard(inputSel.value.slice(inputSel.start, inputSel.end))
+        inputSel.clear()
+
+        return
+      }
+
       if (live.busy && live.sid) {
         return turnController.interruptTurn({
           appendMessage: actions.appendMessage,