Align Squad permission decisions with Copilot CLI v1.0.54+ contract

[Copilot]

Copilot CLI v1.0.54+ changed permission decision kinds, and Squad was still returning legacy values (notably approved), causing tool/shell permission requests to be ignored. This updates Squad CLI + SDK permission handling/types to match the current contract.

• Permission decision contract updates

  • Updated CLI default permission handler to return approve-once instead of legacy approved.
  • Updated SDK guidance/error messaging to recommend onPermissionRequest: () => ({ kind: "approve-once" }).

• SDK type alignment

  • Replaced outdated SquadPermissionRequestResult shape with current decision variants used by Copilot SDK:
    • approve-once
    • approve-for-session
    • approve-for-location
    • approve-permanently
    • reject
    • user-not-available
    • no-result

• Regression coverage

  • Added focused adapter test asserting permission-handler guidance now points to approve-once.

const approveAllPermissions: SquadPermissionHandler = () => ({ kind: 'approve-once' });

[tamirdresher]

Closing in favor of #1192. The regression test from this PR was manually ported to #1192 (commit e1faf5d) without pulling in the SquadPermissionRequestResult type rewrite, which is a breaking API change. The \�pprove-once\ shell fix and error message update are already in #1192. CI passed ✓.