chore: test canvas against json-document RCs

[developer-1px]

Summary

• exact-pin json-document 1.1.0-rc.0 and the three extension packages at 0.1.1-rc.1
• remove the four json-document sibling workspace paths so Canvas exercises the published npm artifacts
• regenerate a single integrity-bearing registry graph and assert the exact RC train in the package manifest contract

Verification

• pnpm install --frozen-lockfile
• physical package/version resolution checks: all four packages resolve through node_modules/.pnpm; no sibling link, external importer, or core 1.0.1 remains
• pnpm run release:check: passed (70 files, 293 focused tests, package smoke, TypeScript and Vite builds)
• pnpm test:e2e: passed (124/124)
• pnpm test: 415 files and 2,120/2,121 tests passed; the sole failure is an existing origin/main design-token violation in FigmaCloneApp.css (margin: -1px). It reproduces in a detached origin/main worktree, and both the CSS and test blobs are unchanged by this PR. Unit tests are not configured as a GitHub Actions PR job; E2E is the configured PR gate.