Add MCP blueprint management tools

[hookdump]

Summary

• Add MCP tools for cancel flow blueprint management:
  • list_blueprints
  • get_blueprint
  • update_blueprint_draft
  • publish_blueprint
• Add MCP tools for cancel flow segment management:
  • list_segments
  • reorder_segments
• Keep writes intentionally split between draft-only updates and explicit confirmed live-impacting actions.
• Document that list_blueprints returns the current flow inventory with compact draft/published metadata, not full historical blueprint payloads.
• Document that passing a published blueprint ID to draft update or publish resolves to the corresponding working copy through the API.
• Restrict draft blueprint updates to supported fields and reject unknown update keys at the MCP schema layer.
• Document the new MCP operations in the README and changelog.
• Add a package-local Vitest harness for @churnkey/mcp.
• Add pnpm test:mcp for local API smoke testing against http://localhost:3000/v1 with --app-id and --api-key flags.

API dependency

Depends on companion API PR: https://github.com/churnkey/churnkey-api/pull/836

Linear

• XDEV-2316 CRUD for Blueprints

Related PRs

• API: https://github.com/churnkey/churnkey-api/pull/836
• SDK: Add MCP blueprint management tools #6 (YOU ARE HERE)
• Docs: https://github.com/churnkey/churnkey-docs/pull/106

Tests

• Blueprint tool unit tests cover endpoint routing, draft update body shape, allowed update schema, invalid brand-image URL rejection, unknown update field rejection, and publish confirmation enforcement.
• Segment tool unit tests cover endpoint routing, reorder body shape, non-empty segment IDs, and reorder confirmation enforcement.
• Query-builder regression tests cover not filter flattening, null/undefined omission, and breakdownBy serialization.

Validation

• pnpm test:mcp --help
• node --check packages/mcp/scripts/test-mcp.mjs
• pnpm --filter @churnkey/mcp test — 3 files / 11 tests passed.
• pnpm --filter @churnkey/mcp typecheck
• pnpm --filter @churnkey/mcp build
• pnpm exec biome check packages/mcp
• Pre-push hook passed full SDK turbo typecheck and turbo test.