Settings UI 'Codex binary path' has no effect

[chuks-qua]

Problem

The Settings UI exposes "Codex binary path" and "Codex home path" fields, but neither value reaches the server. The user can type a custom path, but the server ignores it and always spawns the default codex binary.

Steps to reproduce

1. Open Settings and set a custom Codex binary path (e.g., /usr/local/bin/codex-nightly)
2. Start a new chat session
3. Observe that the server still invokes the default codex binary

Expected behavior

When codexBinaryPath is set in Settings, the server should use that value when spawning Codex CLI commands (both for sessions and health checks).

Relevant files

The server-side plumbing exists but never receives data. The gap is in the orchestration layer:

• apps/web/src/appSettings.ts — stores codexBinaryPath in localStorage
• packages/contracts/src/provider.ts — defines providerOptions.codex.binaryPath schema
• packages/contracts/src/orchestration.ts — ThreadCreateCommand and ThreadTurnStartCommand lack a providerOptions field, so the web app has no way to send the setting
• apps/server/src/orchestration/Layers/ProviderCommandReactor.ts — never reads or forwards providerOptions
• apps/server/src/codexAppServerManager.ts — readCodexProviderOptions() (line ~1510) and startSession() (line ~551) already handle custom paths, but always receive undefined
• apps/server/src/provider/Layers/ProviderHealth.ts — runCodexCommand() hardcodes "codex", ignoring any custom path

[chuks-qua]

Investigation notes

Traced the full data flow from UI to server. The server-side code to consume a custom binary path already works — readCodexProviderOptions() in codexAppServerManager.ts extracts it, and startSession() spawns with the custom path. The contract schema (ProviderSessionStartInput.providerOptions) also exists.

The break is in the orchestration layer: ThreadCreateCommand and ThreadTurnStartCommand in packages/contracts/src/orchestration.ts have no providerOptions field. The web app stores the setting in localStorage but has no channel to send it to the server.

To fix this, the orchestration commands need a providerOptions field, ProviderCommandReactor needs to read it, and ProviderHealth.ts needs to stop hardcoding "codex".