Fix opt-in error responses and SDK documentation

[roncohen]

Summary

• Preserve failed setOptIn() response bodies by logging a cloned response, with regression coverage for readable errors, unchanged membership, and no refresh on HTTP failure.
• Document the complete mutation result contract, explicit loading/Suspense behavior, manual metadata retries, company-scope authorization limitations, and browser-context bootstrap caveats in the Browser/React/Vue SDK docs.
• Correct opt-in JSDoc and add tested Markdown-generation workarounds for imported type aliases and optional properties/parameters, including React Native references.
• Add a Browser SDK patch changeset and verify recovery through refresh() after a failed metadata request.

No authorization enforcement or hook API changes are introduced. Metadata errors remain an API limitation, with documented manual retries rather than a new error/retry API.

Companion documentation

reflagcom/docs#29 updates the public guide and generated SDK references. Publish the Browser SDK fix before relying on readable failed-response bodies in existing installations.

Validation

• Browser client tests: 39 passed.
• React usage tests: 65 passed.
• Vue usage tests: 13 passed (isolated from nested worktrees).
• Documentation postprocessor tests: 3 passed.
• Guide and Browser/React/Vue README examples: all 4 typechecked.
• Browser, React, Vue, and React Native builds; React/Vue type tests; scoped TypeDoc generation with warnings treated as errors passed during implementation.
• Repository lint-staged checks and git diff --check passed.

Based on the latest main; unrelated local changes and management-SDK branch commits are excluded.

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