🤖 fix(openai): omit service_tier when not configured

[ibetitsmike]

Summary

Stop writing serviceTier: "auto" into provider options when the user hasn't configured one, and surface that "unset" state explicitly in the Settings UI and CLI. The provider field is now omitted entirely when no value is selected, letting OpenAI apply its own default routing.

Fixed: #3196

Background

Previously the OpenAI service tier silently defaulted to "auto" everywhere: in buildProviderOptions, in the CLI's --service-tier flag, and in the Settings dropdown. That meant requests always sent service_tier: auto even when the user never picked a tier, and the UI couldn't represent the actual "no preference" state at all (the dropdown showed auto whether the config was missing or explicitly set to auto).

Implementation

• buildProviderOptions now reads muxProviderOptions?.openai?.serviceTier directly and only spreads serviceTier into the OpenAI options when it is set.
• src/cli/run.ts drops the "auto" default from --service-tier; if the flag is omitted, the entire openai block is left out of providerOptions.
• ProvidersSection adds a sentinel "unset" Select item labeled Not configured (omit service_tier). Picking it sends value: "" through setProviderConfig, which the backend treats as a delete, removing the serviceTier key from providers.jsonc. A short-lived openaiServiceTierSelectOverride keeps the trigger label correct between optimistic update and refresh.
• providerModelFactory likewise no longer coerces a missing serviceTier into "auto".

Validation

• Sandboxed dev-server walk-through (clean install -> flex -> back to unset -> explicit auto); each transition verified against providers.jsonc on disk and the dropdown trigger label.
• make static-check (eslint, tsgo x2, prettier, code-to-docs links, shellcheck, hadolint) clean.
• bun test src/cli/run.test.ts src/common/utils/ai/providerOptions.test.ts src/node/services/providerService.test.ts (176 pass).

Risks

Low. Behavior change is limited to OpenAI requests: when no tier was previously configured, requests will now omit service_tier instead of sending "auto". OpenAI treats both as default routing, so live traffic should be unaffected. Existing configs with an explicit value continue to send that value verbatim.

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Generated with mux • Model: anthropic:claude-opus-4-7 • Thinking: xhigh • Cost: $47.05

[ibetitsmike]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Keep it up!

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