fix(tui): honor display.busy_input_mode in TUI v2 (#17110)

* fix(tui): honor display.busy_input_mode in TUI v2

The TUI v2 frontend hard-coded `composerActions.enqueue(full)` whenever
`ui.busy` was true. The classic CLI and gateway adapters honor the
`display.busy_input_mode` config key (`interrupt` | `queue` | `steer`),
but Ink ignored it — sending a message during a long-running turn always
landed in the queue regardless of config. The config default is already
`interrupt` (hermes_cli/config.py), so users who explicitly opted into
that experience were silently stuck on the legacy queue path.

This wires the value through the existing config-sync surface:

* `applyDisplay` now reads `display.busy_input_mode`, defaults to
  `interrupt` (matching `_load_busy_input_mode` in tui_gateway), and
  drops it into a new `UiState.busyInputMode` field.
* `dispatchSubmission` and the queue-edit fall-through call a shared
  `handleBusyInput` helper that branches on the mode:
    * `queue`     — legacy behavior, append to the queue.
    * `steer`     — call `session.steer`; on rejection, fall back to
                    queue with a sys note.
    * `interrupt` — `turnController.interruptTurn(...)` then `send()`,
                    so the new prompt actually moves.
* Mtime polling in `useConfigSync` already re-applies `config.full`, so
  flipping `display.busy_input_mode` in `~/.hermes/config.yaml` takes
  effect on the next 5s tick without restarting the TUI.

Tests:
* `applyDisplay → busy_input_mode` covers normalization + UiState fan-out.
* `normalizeBusyInputMode` mirrors the Python side's allow-list.

Validation:
* `npm run type-check` (in `ui-tui/`) — clean.
* `npm test --run` (in `ui-tui/`) — 394/394.

* review(copilot): narrow busy_input_mode type, preserve queue order on steer fallback

* review(copilot): clarify handleBusyInput comment (option, not return value)

* fix(tui): default busy_input_mode to queue in TUI (CLI keeps interrupt)

In a full-screen TUI users typically author the next prompt while the
agent is still streaming, so an unintended interrupt loses in-flight
typing.  TUI fallback now defaults to `queue`; CLI / messaging
adapters keep `interrupt` as the framework default.

Override per-config via `display.busy_input_mode: interrupt` (or
`steer`) — the normalize/wire path is unchanged, only the missing-
value branch differs from the Python default.

uiStore initial value also flipped to `queue` so first-frame render
before `config.full` lands matches the eventual normalized value.

ui-tui/src/__tests__/useConfigSync.test.ts

@@ -1,7 +1,7 @@
 import { beforeEach, describe, expect, it, vi } from 'vitest'
 
 import { $uiState, resetUiState } from '../app/uiStore.js'
-import { applyDisplay, normalizeStatusBar } from '../app/useConfigSync.js'
+import { applyDisplay, normalizeBusyInputMode, normalizeStatusBar } from '../app/useConfigSync.js'
 
 describe('applyDisplay', () => {
   beforeEach(() => {
@@ -160,3 +160,55 @@ describe('normalizeStatusBar', () => {
     expect(normalizeStatusBar('OFF')).toBe('off')
   })
 })
+
+describe('normalizeBusyInputMode', () => {
+  it('passes through the canonical CLI parity values', () => {
+    expect(normalizeBusyInputMode('queue')).toBe('queue')
+    expect(normalizeBusyInputMode('steer')).toBe('steer')
+    expect(normalizeBusyInputMode('interrupt')).toBe('interrupt')
+  })
+
+  it('trims and lowercases input', () => {
+    expect(normalizeBusyInputMode(' Queue ')).toBe('queue')
+    expect(normalizeBusyInputMode('STEER')).toBe('steer')
+  })
+
+  it('defaults to queue for missing/unknown values (TUI-only override)', () => {
+    // CLI / messaging adapters keep `interrupt` as the framework default
+    // (see hermes_cli/config.py + tui_gateway/server.py::_load_busy_input_mode);
+    // the TUI ships `queue` because typing a follow-up while the agent
+    // streams is the common authoring pattern and an unintended interrupt
+    // loses work.
+    expect(normalizeBusyInputMode(undefined)).toBe('queue')
+    expect(normalizeBusyInputMode(null)).toBe('queue')
+    expect(normalizeBusyInputMode('')).toBe('queue')
+    expect(normalizeBusyInputMode('drop')).toBe('queue')
+    expect(normalizeBusyInputMode(42)).toBe('queue')
+  })
+})
+
+describe('applyDisplay → busy_input_mode', () => {
+  beforeEach(() => {
+    resetUiState()
+  })
+
+  it('threads display.busy_input_mode into $uiState', () => {
+    const setBell = vi.fn()
+
+    applyDisplay({ config: { display: { busy_input_mode: 'queue' } } }, setBell)
+    expect($uiState.get().busyInputMode).toBe('queue')
+
+    applyDisplay({ config: { display: { busy_input_mode: 'steer' } } }, setBell)
+    expect($uiState.get().busyInputMode).toBe('steer')
+  })
+
+  it('falls back to queue when value is missing or invalid (TUI-only default)', () => {
+    const setBell = vi.fn()
+
+    applyDisplay({ config: { display: {} } }, setBell)
+    expect($uiState.get().busyInputMode).toBe('queue')
+
+    applyDisplay({ config: { display: { busy_input_mode: 'drop' } } }, setBell)
+    expect($uiState.get().busyInputMode).toBe('queue')
+  })
+})