docs: polish public docs after alpha.7

[mahyarmlk]

Summary

Polish public-facing docs to accurately present the framework state after alpha.7.

Changes

• README.md: Add examples section listing all 5 examples (canonical-invite, choice-form, resource-lifecycle, secret-vault, web-basic), update roadmap to mark examples trilogy and multi-surface as completed, bump install version to alpha.7, document flow diagnostics
• packages/dom/README.md: Document current renderDom behavior — checkbox/select rendering for boolean/choice asks, multi-surface section output, surface-suffixed DOM ids, duplicate control state sharing, per-surface blocked reasons and feedback
• examples/resource-lifecycle/README.md (new): What it demonstrates, how to run, what to inspect
• examples/secret-vault/README.md (new): What it demonstrates, screens, how to run, what to inspect
• examples/web-basic/README.md (new): What it demonstrates, screens table, how to run
• docs/Quickstart.md: Bump alpha version references to alpha.7
• docs/Release-Readiness.md: Bump all package version refs to alpha.7

Validation

• pnpm lint — ✅ passes
• pnpm changeset status — expected failure (docs-only change, no changeset per task instruction)

Docs-only PR.