chore: drop stale references to the onboarding offer and old resolver

The Playwright project list still named the deleted onboarding AI
offer spec. The CoachPlan comments said the review writes
`outcomeEncrypted` and surfaces it behind a flag; nothing writes or
reads it now, and the column is marked internal. Comments that named
`resolveProvider` as the resolver now name the chain, and the function
itself says it is test-only.

src/components/settings/ai/shared.ts

@@ -127,8 +127,8 @@ export const LOCAL_MODEL_PRESETS = [
 export const CUSTOM_MODEL_SENTINEL = "__custom__";
 
 /**
- * Map UI provider tag → the `aiProvider` enum understood by the
- * legacy single-result `resolveProvider()` resolver. `codex` and
+ * Map UI provider tag → the stored `aiProvider` enum, the provider picked
+ * under Settings, AI. `codex` and
  * `admin-openai` aren't user-level provider columns (they're handled
  * by Codex OAuth + admin-key fallback), so they map to null and the
  * legacy column is left blank.

src/lib/ai/mock-client.ts

@@ -18,8 +18,8 @@ import { reasoningTitleOf } from "./reasoning/support";
  * never hit the network.
  *
  * The mock is exported from `src/lib/ai/` so any test can import it,
- * but it is NOT registered in `resolveProvider()` — the production
- * path must never reach it.
+ * but no provider resolver returns it: the production path must never
+ * reach it.
  */
 export interface MockAIProviderOptions {
   /** Provider tag returned in `CompletionResult.providerType`. Defaults to "local". */

src/lib/ai/provider.ts

@@ -711,7 +711,7 @@ async function resolveAdminCodexProvider(): Promise<AIProvider | null> {
 }
 
 /**
- * Resolve the AI provider for a given user.
+ * Test-only, ignoring the chain's switches: use `resolveProviderChain`.
  *
  * Priority:
  *   1. User selected ANTHROPIC / LOCAL with valid creds → that provider.
@@ -840,7 +840,7 @@ export async function resolveProviderChain(
       aiResponseTimeoutSeconds: true,
     },
   });
-  // See `resolveProvider`: every instance carries the record's settings.
+  // Every instance carries the record's timeout and reasoning effort.
   const bind = (provider: AIProvider): AIProvider =>
     bindReasoningEffort(
       bindResponseTimeout(provider, userRow?.aiResponseTimeoutSeconds),

src/lib/ai/vision-capability.ts

@@ -66,8 +66,8 @@ function openAIFamilySupportsVision(model: string): boolean {
 
 /**
  * Logical provider tags the OCR path reasons about. Mirrors the
- * `ProviderChainType` vocabulary plus the legacy `admin-key` single-provider
- * tag `resolveProvider`'s admin fallback returns.
+ * `ProviderChainType` vocabulary plus the legacy `admin-key` tag the
+ * operator-key client carries.
  */
 export type VisionProviderType =
   | "anthropic"