docs: make the live pairing helper the desktop entry

[veil-chow-fyaic]

Delivered

• Put the deployed no-install pairing helper in English and Chinese README and guides.
• Preserve an actual public-page screenshot and the generated-prompt API case: original B updated its own client and tests, retaining prior constraints.
• Update status, roadmap and evidence indexes without claiming automatic connection or independent GUI onboarding.

Verification

• Documentation lint: 149 files, no issues; git diff --check clean.
• Helper implementation and 14 regression tests already merged in Ship a no-install bilingual pairing helper for existing Codex tasks #174; deployed assets match source.
• API case independently reviewed; both original test tasks stopped.
• Native transport belongs to Codex; incremental benefit remains unmeasured.