feat: add durable inbox delivery notices

[coldlogicAI]

Summary

• Add plain-text delivery notices to CLI/MCP send results so agents can forward inbox work through text channels.
• Add read-only delivery status checks via notch inbox status <delivery-id> [--at local:name] and MCP get_inbox_delivery.
• Update docs, prompt instructions, schemas, tests, and bump package version to 0.7.0.

Verification

• npm run type-check
• npm run lint
• npm test
• npm run test:e2e
• npm run build
• node dist/cli/index.js --version
• node dist/cli/index.js inbox --help

[coldlogicAI]

Follow-up cleanup pushed

Addressed the review nits before merge:

1. Status nextAction coverage — unit tests now assert sender-side getInboxDeliveryStatus for pending, pulled (verify-only), pulled+imported, acked, and rejected (hash mismatch fixture).
2. Wording — docs/guides/mcp-setup.md and agent prompt (src/cli/prompts/shared.ts) now include pending in the get_inbox_delivery description.
3. MCP output schema — notice is gated with includeIdempotent so only send_packet advertises it; pull/ack schemas no longer list an unused optional notice.

Commit: db16ded