Switch the development mode. Usage: /catalyst-dev-mode framework or /catalyst-dev-mode solution

Valid values: "framework" or "solution" (case-insensitive).

The mode file lives at the project root (`.catalyst-dev-mode`), not in the user home directory.
See the "Development Modes" section in CLAUDE.md for the full description of each mode.

## Behavior

### 1. If $ARGUMENTS contains a valid value (`framework` or `solution`, case-insensitive)

1. Read the current mode from `.catalyst-dev-mode` in the project root.
2. If the requested mode equals the current mode, confirm with a one-line message ("Already in
   <Mode> mode.") and stop.
3. Otherwise, write the normalized mode ("Framework" or "Solution") to `.catalyst-dev-mode` and
   confirm the switch with a one-line message.

### 2. If $ARGUMENTS is empty

1. Read the current mode from `.catalyst-dev-mode` in the project root.
2. Use the `AskUserQuestion` tool to present a selector with both modes. The question MUST:
   - Header: `Dev mode`
   - Question: `Current mode is <Current>. Select the mode to switch to:`
   - Multi-select: `false`
   - Options (in this order):
     - label: `Framework`, description: `Build reusable tools, patterns, and architecture for future consumers.`
     - label: `Solution`, description: `Implement concrete requirements using existing architecture; shortest path.`
3. After the user picks an option:
   - If the picked mode equals the current mode, reply with one line: "Already in <Mode> mode." and
     stop without writing the file.
   - Otherwise, write the normalized mode ("Framework" or "Solution") to `.catalyst-dev-mode` and
     confirm the switch with a one-line message.

### 3. If $ARGUMENTS is non-empty but invalid

Reply with a one-line error showing the valid values (`framework`, `solution`) and the current
mode. Do NOT change the file.

## Notes

- Always preserve the canonical capitalization in the file: `Framework` or `Solution` (no other
  variants).
- Do NOT run any other command, lint, format, or commit step. This is a single-file write only.
- Do NOT echo the file contents; the one-line confirmation is enough.
