Fix Codex Fast-mode defaults for Business accounts

[wizzoapp]

Summary

Fix Codex service-tier defaults for eligible ChatGPT Business/Enterprise accounts without removing Fast from the selector.

Root cause: T3 copied model/list.defaultServiceTier directly into every new composer and did not read the provider instance's effective config/read result. It could therefore overwrite an explicit Standard choice or the durable [notice] fast_default_opt_out = true marker with the catalog-managed Fast default. Request construction also needed to preserve an explicit clear value instead of relying on omission.

The fix keeps catalog defaults, configured preferences, and per-thread selections distinct:

• reads config/read through each Codex provider client/home before mapping that instance's model catalog
• resolves explicit config/opt-out before the catalog-managed default, while preserving saved draft/thread choices
• normalizes legacy fastMode and string fast selections to canonical priority
• retains Standard, Fast, and Flex availability and sends selected tiers on start, resume, subsequent turns, and helper invocations
• clears unsupported configured tiers to explicit Standard instead of falling through to catalog Fast

Protocol

Confirmed against Codex 0.145.0 and current upstream source: Standard is the explicit request sentinel serviceTier: "default". App-server accepts null as a clear input but normalizes it to "default"; T3 therefore transmits the current canonical string and never omits Standard. Helper codex exec calls use --config service_tier="default".

Verification

• focused server/web/shared unit/integration suite: 7 files, 138 tests passed
• mobile/shared/web normalization regression suite: 3 files, 37 tests passed
• targeted formatting/lint passed
• focused server/web/shared typechecks passed
• desktop web/server asset build passed
• factory pre-commit gate passed repository static checks and a clean Codex review after all accepted findings were fixed
• isolated real Codex config/read probe confirmed opt-out and explicit Standard shapes; config checksum remained unchanged after reads
• ephemeral real T3 web UI with a controlled ChatGPT Business app-server: catalog Fast default + opt-out displayed Standard; captured thread/start, first turn/start, and resumed second turn/start all contained explicit serviceTier: "default"

Coverage includes all requested cases: opt-out, explicit Standard, no-config managed Fast, explicit Fast, Flex, Fast→Standard persistence, saved Standard draft, legacy fastMode:true, non-eligible Standard fallback, and independent Windows/WSL provider config reads.

Windows/WSL: test-covered, NOT yet live-exercised (VM blocked).

[adamfgr]

Auto-approved by wizzo-approve: all policy conditions verified against HEAD 1b7df62.