Support true read-only mode for Gmail and Calendar connectors

Feedback

Codex needs a true read-only mode for Gmail and Calendar connectors.

Current problem:

• Users who want Codex for chief-of-staff style automations need mail/calendar context, but do not want the agent to have any ability to send mail, mutate labels, archive messages, create/update/delete calendar events, or RSVP.
• The connector/tool surface can expose mutation tools. For Gmail, examples include message label modification and bulk label/archive operations. For Calendar, the concern is event create/update/delete/respond capability.
• Relying on agent behavior to voluntarily avoid write tools is not a strong enough trust boundary for inbox and calendar access.

Requested behavior:

1. Offer a first-class read-only connection mode for Gmail and Calendar.
2. In read-only mode, request only read-only OAuth scopes, for example Gmail gmail.readonly and Calendar read/freebusy scopes.
3. Hide or disable all write-capable tools from the model-visible tool surface when read-only mode is selected.
4. Make the permission mode visible in the UI so users can verify what the agent can and cannot do.
5. Ideally support custom remote MCP OAuth configuration where users can provide a client and explicit scopes for services like Google Workspace MCP.

Why this matters:

The main use case is recurring automations such as daily briefs, pre-call prep, follow-up reminders, and inbox/calendar triage. These are high-value, but many users will not connect Gmail or Calendar unless the platform provides a hard read-only permission boundary comparable to products that already expose read-only Google access.

A read-only connector mode would make Codex usable for personal productivity and founder/operator workflows without requiring users to grant unnecessary write permissions.