Feat: allow permanently skipping the /goal start permission prompt ("don't ask again")

Feature request

When starting a goal with /goal <objective> in yolo (or manual) permission mode, the TUI always shows the "Start a goal in YOLO mode?" confirmation dialog (options: Switch to Auto and start / Keep YOLO and start / Do not start).

There is currently no way to opt out: no config key in config.toml / tui.toml, no environment variable, and no "don't ask again" choice in the dialog itself. Users who always want the same answer have to confirm every single goal.

Requested behavior

Any one of these would work:

• A "don't ask again" / "always keep YOLO" choice in the dialog that persists (for example under ~/.kimi-code)
• A config key, e.g. goal_start_prompt = false or a [goal] section option in config.toml
• Respect default_permission_mode as the pre-approved answer and skip the prompt when it was explicitly configured

Why

Users who deliberately run in yolo mode have already accepted auto-approval of tool actions. The extra per-goal prompt adds a manual step to an otherwise autonomous workflow, especially when queuing goals regularly.

Environment

• kimi-code CLI version: 0.29.1
• OS: macOS
• Permission mode: yolo (set as default_permission_mode in config.toml)

Start at the /goal entry point and locate the TUI confirmation dialog described in the issue. Read how default_permission_mode is loaded from config.toml, then determine which requested persistence or configuration behavior fits the existing flow; done means a deliberate user choice or explicit setting prevents the prompt on later goal starts while other modes retain it.