[FEATURE] Allow scheduled tasks on a repo to return a text-only response without creating a branch

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

When a scheduled task is attached to a repo, it currently creates a branch as part of its run, even when the task is purely read-only and the only desired output is a text summary. Common examples:

• Daily PR digest ("summarize open PRs and their review status")
• Weekly issue triage report
• Recurring repo health check
• Daily standup-style summary of recent commits

Proposed Solution

Add a per-task option (e.g. a "Read-only / text response only" checkbox in the scheduled task setup) that:

1. Skips branch creation entirely for that task.
2. Disables repo write tools for the run (no commits, no pushes, no PR creation).
3. Returns the task's output as a plain text session, the way a normal chat response works.

A per-task setting feels right here — some scheduled tasks legitimately need to write to the repo, others don't, and the user knows which is which at creation time.

Alternative Solutions

_No response_

Priority

Low - Nice to have

Feature Category

Interactive mode (TUI)

Use Case Example

_No response_

Additional Context

Combined with #46618 (completed scheduled task sessions appearing in the Today list), this would make recurring text-output tasks like daily digests behave just like normal sessions: fire on schedule, drop a readable result into Today, no repo cleanup required.