[Bug]: Auto-accept keybind (Cmd+Shift+A) dead on New Session screen and when switching projects #16258

Description

The Cmd+Shift+A keybind for toggling auto-accept permissions has two bugs:

1. Dead on New Session screen: The keybind is disabled when no session is active (disabled: !params.id), so pressing Cmd+Shift+A on the "New session" screen does nothing. The chevron icon also doesn't reflect auto-accept state.

2. Dead after switching projects: When permission: "allow" is set in the global opencode.json, permissionsEnabled() returns false (since there are no non-allow rules to prompt for), which gates the keybind with disabled: !permission.permissionsEnabled(). This makes the keybind permanently dead for users with permission: "allow".

Steps to Reproduce

1. Set "permission": "allow" in ~/.config/opencode/opencode.json
2. Open OpenCode desktop, navigate to any project
3. Press Cmd+Shift+A — nothing happens
4. Start a session, press Cmd+Shift+A — still nothing
5. Switch to another project — keybind remains dead

Expected Behavior

• Cmd+Shift+A should toggle auto-accept regardless of the permission config
• On the "New session" screen, it should toggle at the directory level
• The chevron icon should reflect the current state
• When permission: "allow" is configured, auto-accept should be on by default

Related: #7928, #1813