#7796: Enable model login with OpenAI device code

## Purpose In a remote access setup, such as a Docker environment, it is easier to use device code to log in to the OpenAI Codex account. The current codebase didn't support it, and this PR added this feature. ## Changes When mode (open-device-code) is selected, run `codex login --device-auth` with runCommandWithTimeout to print the code on the terminal. However, stdout and stderr default to "pipe", so device-code login was hanging without showing the URL/code because stdout/stderr were piped. We need to change them to inherit. - Add `inheritChildStdOut` option to `runCommandWithTimeout`. - Extend `resolveCommandStdio` to allow optional stdout/stderr inheritance. ## Tests - `src/process/spawn-utils.test.ts` to test the behaviors of `runCommandWithTimeout` and `resolveCommandStdio,` when setting inheritChildStdOut to True and False (should stay the original results when being False). - For the end-to-end tests on the login using a real account and the device code, we tested manually. <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR adds an interactive onboarding option `openai-device-code` that runs `codex login --device-auth` to support OpenAI/Codex login in remote environments (e.g., Docker), and extends process spawning utilities to optionally inherit child stdout/stderr so the device URL/code is visible. Key wiring changes include new auth choice option/group entries and preferred provider mapping, plus a new `inheritChildStdOut` flag on `runCommandWithTimeout()` that routes through `resolveCommandStdio()`. Main concern: with inherited stdout/stderr, `runCommandWithTimeout()` can no longer collect output into `SpawnResult.stdout/stderr`, but the new device-code path still assumes it can show captured output on failure. There’s also a test coverage regression where `spawnWithFallback` tests were removed entirely. <h3>Confidence Score: 3/5</h3> - Reasonably safe to merge, but error reporting for device-code login failures is likely misleading when stdio is inherited. - The feature is straightforward and localized, but changing stdio behavior introduces a real semantic mismatch: inherited stdout/stderr cannot be captured, yet callers still treat `stdout/stderr` as available. Also, test coverage dropped for `spawnWithFallback`, reducing confidence against regressions in process spawning. - src/process/exec.ts; src/commands/auth-choice.apply.openai.ts; src/process/spawn-utils.test.ts <!-- greptile_other_comments_section --> _{(2/5) Greptile learns from your feedback when you react with thumbs up/down!} <!-- /greptile_comment -->