Add /draft Draft Something workflow shell

Adds a frontend-only drafting flow that mirrors the /review pattern
from PR #8. Reuses the existing assistant chat plumbing - no new
backend routes, no API contract changes.

- New route at /draft with a 3-step lawyer-friendly UI:
    1. Choose draft type (8 cards: Email, Letter, Memo, Clause,
       Summary, Demand letter, Client update, Custom draft, each
       with plain-English helper copy)
    2. Add details (description textarea with the suggested
       placeholder; optional Audience / Tone single-line fields;
       optional Attach a document via existing
       uploadStandaloneDocument; lawyer-facing caution box)
    3. Review draft (handed off to the assistant chat)
- Start Drafting builds a MikeMessage from the option's opening
  line + the user's description + optional metadata, appended with
  the default tail instruction:
    "Draft the requested legal document using the facts provided.
     Be clear, organized, and practical. Do not invent facts.
     Flag any missing information that would be needed before
     finalizing."
  Then reuses useAssistantChat.handleNewChat + router.push to the
  same /assistant/chat/{id} path used by /review and the home.
- Updates the Gary-mode "Draft Something" card to point at /draft
  instead of /workflows. /workflows is unchanged.

No backend changes, no auth/billing/teams, no new providers.
License unchanged.

https://claude.ai/code/session_019pRkhcGDRKQWHjzAnV5yCL