fix(cli): improve init diagnostics and starter output

[mldangelo]

Summary

Stacked on #742 (base mdangelo/codex/project-configuration), so it can be reviewed in parallel and will retarget to main when that lands. Four follow-ups to the init command added in #742, all cosmetic except the last.

• Refusing to overwrite is init's advertised behavior, so it now reads as a sentence naming the file rather than a raw errno. Before: codex-security: EEXIST: file already exists, open '/…/codex-security.yaml'. After: codex-security: /…/codex-security.yaml already exists. Edit it, or select it with --config codex-security.yaml.
• Write the starter with default permissions instead of 0o600. The file holds no credentials and is meant to be committed; the private mode only broke shared checkouts and containers running as another user.
• JSON starters cannot carry the commented settings a YAML starter shows, so init file.json previously produced a file whose entire content was a $schema key. It now prints that guidance to stderr and points at the YAML template. The file itself is unchanged.
• Search upward from the starter for an installed @openai/codex-security so hoisted workspaces get an editor hint that resolves, falling back to the invocation directory when nothing is installed yet. This is the one behavioral change; the docs previously recorded the old behavior as a limitation and are updated to match.

projectConfigStarter now returns { contents, notes } so the "what guidance does this format need" decision stays next to the YAML comment block. It has one call site and is not exported from index.ts.

Testing

• bun test ./tests-ts/cli-project-config.test.ts: 52 passed, no failures. Three new cases cover the umask permissions (compared against a reference write, so the assertion holds under any umask), the JSON guidance, and the hoisted-workspace $schema. The existing overwrite case now also asserts the message and that EEXIST no longer appears.
• bun test across cli-project-config, project-config, sdk-project-config, deep-config, cli, skeleton: 279 passed, 1 failed. The failure is skeleton.test.ts "keeps machine-wide policy changes out of parallel and experimental runs", which fails identically on main in this environment (Bun.YAML.parse on bun 1.3.3 mis-parsing the workflow on: key) and is unrelated to this change.
• pnpm run types and prettier --check: pass.
• Verified against a built CLI in a scratch workspace with node_modules hoisted to the root and the starter written to packages/app/: the second init prints the new sentence and exits 2, the file is -rw-r--r--, the JSON starter prints both guidance lines to stderr, and the nested starter emits $schema: ../../node_modules/@openai/codex-security/schemas/project-config.schema.json.

Risk and rollout

No shared types, resolution logic, or precedence rules change, and nothing in #742 depends on projectConfigStarter's shape. The permissions change makes a previously owner-only file world-readable subject to umask; that matches how tracked configuration is normally created and the file is documented as never holding credential values.

The $schema search reads the filesystem during init only. Existing behavior is preserved when nothing is installed, which is the common case for a first run before npm install.

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[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-01T07:20:11.051966Z	9226185	PR opened
🔒 Security Review	✅ Completed 2026-09-01T07:21:09.360748Z	9226185	PR opened

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