Correct opt-in loading, error handling, and authorization guidance

[roncohen]

Summary

• Explicitly enable Suspense in the quick start, handle both loading states without Suspense, and avoid treating unavailable metadata as an authoritative empty list.
• Handle skipped/non-OK mutation responses and promise rejections, and add a reload example with independent pending/error state.
• Document the publishable-key/company-scope trust model, confirmation failures after remote changes, conditional bootstrap metadata refreshes, and browser-context re-evaluation caveats.
• Synchronize Browser/React/Vue SDK examples and fix opt-in reference types for Browser/React/Vue/React Native, including the duplicate React README.

Preserves the latest guide restructuring, prerequisites, and handbook links on main. No authorization enforcement or hook API changes are implied; metadata failures use documented manual retry.

Companion SDK change

reflagcom/javascript#729 preserves readable HTTP error responses, adds regression coverage, and makes the reference-generation fixes durable. Publish that SDK change before relying on readable failed-response bodies in existing SDK installations.

Validation

• All four updated guide/SDK README examples typechecked.
• Opt-in reference sections matched the corrected generated output during implementation.
• Companion SDK validation: 117 targeted SDK tests and 3 documentation tests passed, plus SDK builds, type tests, and scoped TypeDoc generation.
• git diff --check passed.

Only opt-in documentation changes are included; unrelated local API docs and assets are excluded.

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