Show enhancement availability in terminal and desktop interfaces

## Problem

Users cannot currently see whether AI-enhanced suggestions are available for the active set. Offering the control for an unenhanced set would imply that the feature is active when no compatible enrichment exists.

## Proposed change

Render shared enhancement availability consistently in the TUI, plain-watch output, and PySide6/QML desktop interface.

When available, identify the active profile as AI-enhanced and provide the enable/disable control. When unavailable, show a concise set-specific message and disable or omit the control.

Make clear that the profile was enhanced offline; no model is called during the live draft.

Keep all availability and command behavior in the shared session. Frontends remain presentation adapters.

## Acceptance Criteria

- [ ] AC1: `tests/test_tui.py` verifies available, enabled, disabled, and unavailable enhancement states and user commands.
- [ ] AC2: `tests/test_watch.py` verifies that plain-watch output identifies enhanced suggestions when active and does not claim enhancement for unenhanced sets.
- [ ] AC3: `tests/test_qt_adapter.py` verifies immutable session-state translation and enable/disable command dispatch.
- [ ] AC4: `tests/test_qt_gui.py` verifies that the desktop control is available only for enhanced profiles and that unavailable copy includes the active set.
- [ ] AC5: TUI and desktop wording states that enrichment is profile-backed and does not imply live AI processing.
- [ ] AC6: The actual terminal and desktop workflows are visually exercised with enhanced and unenhanced mock profiles.
- [ ] AC7: Core and session modules remain free of Textual, PySide6, QML, and presentation-specific dependencies.

## Dependencies

- Expose enhancement availability through the live session.

## Implementation classification

- **Estimated size:** M
- **Orchestration risk:** High
- **Reason:** The same availability contract must remain consistent across terminal and desktop surfaces.

Start with the shared live session and the interfaces named in the issue, then read tests/test_tui.py, tests/test_watch.py, tests/test_qt_adapter.py, and tests/test_qt_gui.py. Verify the availability states and command dispatch in those tests, then visually exercise enhanced and unenhanced mock profiles as described in the acceptance criteria.

索引モデルが issue の本文から書いたものです。