docs: lead README with Vite plugin path

[kevinccbsg]

Summary

• Vite Quick start is now the first content section — install + add twdRemote() to vite.config.ts + npx twd-relay run. The manual createBrowserClient snippet is gone from the top.
• Manual setup demoted to a clearly-framed "non-Vite, or opting out" section below operational reliability. Targets Webpack / Angular CLI / Rollup / esbuild / Rspack consumers and Vite users who explicitly set autoConnect: false. Includes the inline double-client warning.
• Failures recap promoted to its own subsection under "Operational reliability" (was a one-line note at the bottom of CLI run command).
• --max-test-duration flag added to the CLI flags table — it was supported by the CLI but missing from the docs.
• Architecture and protocol moved below the practical sections — they're reference, not need-to-know.

No code changes. Net: 139 insertions / 111 deletions, README only.

Test plan

• Render the PR README on GitHub and confirm the "Quick start (Vite)" section is the first thing readers see after the tagline.
• Verify the [CLI run command](#cli-run-command) anchor inside Quick start resolves correctly on GitHub.
• Verify the manual setup section's src/browser/types.ts link points at the right file.

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