Refresh bilingual README and user-first documentation

[veil-chow-fyaic]

Reader outcome

Make the English and Chinese entry points explain the same current product:
ordinary independent sessions cooperate without human relay, with explicit
limits and useful first-use instructions.

Changes

• Lead both READMEs with the real Codex→same-Pi sequence and show the retained
  API pass, no-contact pass and copy-quality failure together.
• Match command blocks, versions, evidence and capability boundaries across
  languages; retain the existing clearly labelled concept illustration.
• Add a Chinese first-workspace guide and a reproducible repo-only fixture
  path. Clarify that the public launcher does not create application files.
• Refresh both documentation indexes and product guides. Move historical
  five-role/adapter experiments out of the current first-use path.
• Preserve the distinction between no-model preview, live model behavior,
  message receipt and business correctness; no new product claims or runtime changes.

Validation

English/Chinese command blocks and version/evidence markers compared directly.
Markdown lint and local regression tests, followed by CI/link checks before merge.
No new live-model calls or changes to the retained evidence.