fix: close privacy and release blockers - #433

Summary

• Validate full MCP packets and prevent page callers from overriding host-owned privacy policy.
• Apply user-source sanitization to state, refresh React sanitizers, and make focus sources SSR safe.
• Preserve parseable JSON under prompt budgets and reuse the cancellation fix from fix(core): honor source abort signal without timeout #432 with its original authorship.
• Bundle the extension content script as a standalone classic script and add real unpacked-extension tests.
• Patch MCP runtime, dashboard, and React scaffold dependencies; monitor and audit standalone examples.
• Test isolated npm tarballs in CI and immediately before publishing.
• Document upgrade requirements and bump all packages to 0.17.2 in a separate version-only commit.

Verification

• Full workspace builds pass.
• 1,341 unit tests pass across the workspaces (Node 26 needs NODE_OPTIONS=--no-experimental-webstorage).
• Chromium, Firefox, and WebKit capture tests: 134 passed, 1 skipped.
• Extension: 10 build checks and 2 unpacked Chromium tests pass.
• Packed context/core/bridge/mcp artifacts: 11 public API checks pass; negative export and origin fixtures verify that the checker fails closed.
• Dashboard production build passes; npm and pnpm audits report no known vulnerabilities.
• Root production and docs audits report zero vulnerabilities.
• Versioned docs build and browser review pass.

Release notes

Examples deliberately remain on the published ^0.17.1 range until npm publication succeeds. Merge with commits preserved, then verify the tag, publisher runs, and downloaded npm artifacts. Angular development tooling and React Native example dependency alerts remain separate follow-up work; this is not an assertion that the entire Dependabot backlog is clear.

No launch or campaign assets are included.

Fixes #366.
Fixes #376.
Fixes #391.