Allow plan mode to override --dangerously-skip-permissions when toggled

Feature Request

When starting Claude with --dangerously-skip-permissions, plan mode is available in the shift+tab mode cycle, but it doesn't actually enforce its restrictions. Claude can still edit files without permission even when plan mode is selected.

Desired Behavior

When toggling to plan mode via shift+tab, it should enforce read-only restrictions regardless of whether --dangerously-skip-permissions was used to start the session. This would enable a binary workflow:

• Dangerous mode: Execute freely without permission prompts
• Plan mode: Read-only exploration until the user approves a plan

Users could shift+tab to toggle between these two modes within the same session.

Current Behavior

--dangerously-skip-permissions is a global override that bypasses all permission checks, including plan mode restrictions. Even when plan mode is visually selected, Claude can still edit files.

Use Case

This enables a clean workflow where users can:

1. Start with --dangerously-skip-permissions to have the dangerous mode available
2. Toggle to plan mode when they want Claude to propose changes before executing
3. Toggle back to dangerous mode when ready for Claude to execute freely

Without this, users must choose between having dangerous mode available (but no enforced planning) or having enforced planning (but no quick toggle to auto-execute).