[P5][MESH-04] Mobile and additional presentation clients

Programme: #1
Epic: #31

## Objective
Extend the personal runtime to mobile/additional clients for capture, reading, approvals and handoff without assuming desktop-level control capabilities.

## Scope
- Mobile workspace browsing/reading, search, evidence inspection and notifications.
- Voice capture/dictation using the shared speech/context model.
- Approval/rejection for pending trusted actions with exact proposal context.
- Device-to-device handoff of workspace/object/task selection.
- Explicit client capability negotiation and support matrix.
- Mobile-specific local storage, biometric/device-key integration where appropriate and revocation.
- Later experimental clients (spatial/embedded) behind the same presentation contracts.

## Security/product rules
- Mobile pairing does not inherit desktop filesystem or PC-control grants.
- Approval UI remains trusted native/runtime chrome, not generated content.
- Sensitive data sync follows MESH-01 scopes and device security state.

## Acceptance criteria
- [ ] Mobile client can inspect synced workspaces/evidence and hand off context to a desktop/runtime worker.
- [ ] Voice capture is clearly indicated and follows configured audio retention.
- [ ] Approval action shows exact account/target/amount/audience and rejects stale proposals.
- [ ] Client capability matrix prevents desktop-only actions from appearing executable on unsupported devices.
- [ ] Revoked/lost device loses future sync/approval authority.
- [ ] Handoff preserves object/task identity without transferring unrelated private context.

## Dependencies
- MESH-01
- VOICE-01

**First phase:** P5
**Maturity target:** P7
**Owner:** platform

No implementation files or tests are identified. Start by reading the dependencies MESH-01 and VOICE-01, then map the mobile presentation contracts, capability matrix, pairing, sync, approval, and handoff requirements. Done means all listed acceptance criteria are implemented, including revocation and protection from unsupported desktop-only actions.

Written by the indexing model from the issue text.