docs(architecture): audit Model access group against implementation

[ggbdpq]

Summary

Audits the Model access group (2 documents) from #3522 against the current implementation, one PR for the group as requested.

• docs/architecture/openai-responses-incremental-transport.md — every named symbol resolves in the current source: the session-fallback promptCacheKey (maka:${sessionId}) where an explicit caller value wins (packages/runtime/src/openai-responses-continuation.ts:99), the turn-scoped continuation lane in ModelAdapter (model-adapter.ts:145), endLane and the five-minute cross-turn socket cooldown (openai-responses-websocket.ts:118,34), and the sdk.response.messages replay contrast (openai-responses-continuation.ts:37). No drift found, so the only change is the standard frontmatter with last_verified.
• docs/model-metadata-firstscreen-optimization.md — the described optimization is implemented: onboarding:getSnapshot exists, the credential projection is conservatively hasSecret: false (onboarding-service.ts:217), the onboarding hero copy is metadata-free, and the renderer startup chain (app-shell.tsx → use-shell-chat-model.ts → shell-chat-model-selection.ts) carries no runtime metadata import; PROVIDER_REGISTRY remains only under lazy settings paths. The Problem section is therefore now explicitly marked as the 2026-08-04 pre-optimization record, in both languages. One real drift fixed: the cited renderer file chat-model-selection.ts is actually shell-chat-model-selection.ts.

The drift-grep recipes from the tracking issue (run\.json, events\.jsonl, runtime-events\.jsonl, PermissionEngine, respondToPermission, agent-run-store\.test\.ts) return zero matches in both documents.

Verification

Claim	Command / route	Result
Diff is docs-only and scoped to the group	git diff --stat on this branch	2 files, +32/−2
Formatting	npm run format:check	exit 0, 1,942 files clean
License headers	npm run check:asf-headers	all tracked files pass; the only flagged file is my machine's local untracked .gitkeep scratch file, not part of this PR
Symbols in the OpenAI transport doc	grep over packages/runtime/src	all resolve (line refs in Summary)
Startup chain metadata-free	import tracing in apps/desktop/src/renderer	shell-chat-model-selection.ts has zero non-type imports
Drift-grep recipes	the six patterns from the tracking issue	zero matches in both documents

Left untouched on purpose: the point-in-time records (the 2026-08-04 chunk-size tables; the "34 passed" and "3,217 tests" runs in the OpenAI doc's Verification outcome) are historical results of earlier runs and stay as written.

AI use

Prepared with ZCode (GLM-5.3-Flash): the agent read both documents and the current source, traced each claim above to files and lines, and drafted the edits. The commit carries the Generated-by trailer.

Checklist

• One subsystem group only (Model access, 2 documents)
• Refs #3522 in the commit message
• Translations move together (single bilingual file; EN and ZH sections changed in lockstep, translation_status: synced)
• last_verified set to the audit date (2026-09-04)
• Docs only, no code changes