* feat(tools): add outputSchema with structuredContent to all tools
## Summary
Declares `outputSchema` (Zod JSON Schema) and returns `structuredContent` on every MCP tool so that clients can consume typed, structured output in addition to the existing JSON text blocks. This is purely additive — existing clients continue to work unchanged.
## Changes
- **`src/tools/index.ts`**
- Updated `ok()` helper to accept an optional `structuredContent` param
- Defined shared output schemas: `accountSummaryOutputSchema`, `emailSummaryOutputSchema`, `emailAddrOutputSchema`, `attachmentMetaOutputSchema`, `styleOutputSchema`
- Added `outputSchema` to all 15 tools — discriminated union for `add_account` (pending vs ready states)
- All handlers now return `structuredContent` alongside their existing JSON `content` block
* merge: resolve conflicts with main — integrate draftHtml into outputSchema