fix(accounts): guide ChatGPT route setup

[tcballard]

Summary

Implements WF-ROADMAP-0015 desktop v0.1.0 ChatGPT account setup guidance.

Adds:

• a dedicated setup-required state when the optional ChatGPT route has not been configured;
• plain-language numbered guidance with copyable configuration and direct config/settings actions;
• regression coverage that keeps missing setup distinct from gateway failures.

Scope

Included

• Replace the red “Could not check ChatGPT” failure shown for HTTP 404 with an intentional onboarding state.
• Provide Copy Configuration, Open Config, Gateway Settings, and Check Again actions.
• Explain that ChatGPT remains opt-in and does not change Automatic routing.
• Remove implementation terminology from normal error copy while retaining the exact provider configuration where it is needed.

Excluded

• Silently editing or replacing an existing gateway configuration.
• Automatically restarting the gateway.
• Changing routing defaults, credential handling, provider isolation, or the ChatGPT runtime trust boundary.

Product / Architecture Decisions

• A missing optional route is setup state, not an operational failure.
• Wayfinder does not mutate an existing TOML file because doing so could overwrite user-owned gateway configuration.
• The exact reviewed chatgpt-sol configuration remains visible and selectable for advanced setup.
• Retry remains available only as “Check Again” after the required setup actions are explained.

User-Facing Contract

CLI

No CLI changes.

Human Output

Accounts now says “Add ChatGPT to Wayfinder” and presents three concrete steps. The user can copy the configuration, open the actual config file, jump to Gateway Settings to restart, and return to check readiness.

JSON Output

No JSON changes.

Exit Codes

No exit-code changes.

Verification

Ran

env CLANG_MODULE_CACHE_PATH=/private/tmp/wayfinder-accounts-ux-module-cache SWIFTPM_MODULECACHE_OVERRIDE=/private/tmp/wayfinder-accounts-ux-module-cache WAYFINDER_DISABLE_SWIFTPM_SANDBOX=1 swift test --disable-sandbox --scratch-path /private/tmp/wayfinder-accounts-ux-build --package-path macos/WayfinderMac

git diff --check

Covered

• 172 Swift tests passed with zero failures.
• HTTP 404 maps deterministically to setup-required rather than failed.
• Runtime unavailable, reauthentication, generic failures, login, cancel, and logout remain distinct.
• No manual app interaction was performed; maintainer screenshot review is intentionally deferred.

Review Path

1. CodexAccountSettingsState.swift for the new setup-state classification.
2. AccountsSettingsView.swift for copy, hierarchy, and actions.
3. CodexAccountClient.swift for user-facing 404 copy.
4. Account state/client tests for regression coverage.

Notes For Reviewer

This PR is stacked on PR #106, which contains the ChatGPT provider and the merged routing-popover UX. Retarget or rebase onto main after #106 lands.