feat(translate): expand namespace tools and carry reasoning in compat adapters

[caigee-cmd]

What

Three grouped changes on this branch:

1. feat(translate): namespace tool expansion + reasoning replay (internal/translate, internal/providers/{trae,workbuddy})
   • New NormalizeOpenAITools: expands Codex/Desktop namespace tool wrappers into flat OpenAI function tools, qualifies nested names as namespace__name (already-qualified mcp__* untouched), and drops hosted shells (mcp / web_search / web_search_preview).
   • Wired into the Responses translator, the Trae payload normalizer, and the WorkBuddy payload normalizer so all three accept the same tool shapes.
   • Responses input now replays one model turn as a single assistant message: reasoning items stay pending and attach to the next assistant message / function_call as reasoning_content; adjacent assistant items merge (content, reasoning_content, tool_calls).
   • function_call_output accepts content-block arrays and lifts input_image blocks into a following user message.
   • WorkBuddy keeps reasoning-only assistant turns; ChatMessage gains reasoning_content.
2. docs(agents): AGENTS.md doc map gains a read-when column and points at docs/ARCHITECTURE.md / docs/REQUEST.md; both added to .gitignore (kept local, not published).
3. docs: zh/en READMEs de-duplicated and aligned to the same section order and length.

Checks

• go build ./... — pass
• go test ./... — pass
• go vet ./... — pass
• python3 scripts/release-notes.py self-test + validate — pass
• gofmt clean on all touched files (3 files were unformatted and are now fixed; the 5 remaining dirty files are pre-existing on main and untouched here)

Notes

• docs/ARCHITECTURE.md and docs/REQUEST.md exist on disk with frontmatter but are not committed — they are gitignored, matching DESIGN.md / PLAN.md.