docs: Add Permission Handling section to all language READMEs

[Copilot]

onPermissionRequest is a required parameter when creating or resuming sessions, but it was undocumented in the config tables and absent from all Quick Start examples — causing confusing runtime errors for new users.

Changes

• All 4 READMEs (Node.js, Go, Python, .NET)
  • New ## Permission Handling section covering: built-in approve-all helper, custom per-kind handlers, result kind reference table, resume session usage, and cross-reference to per-tool skipPermission
  • Added onPermissionRequest / OnPermissionRequest / on_permission_request as Required in SessionConfig and ResumeSessionConfig docs
  • Updated Quick Start examples to include the required handler

Per-language API

Language	Approve-all helper	Custom handler type
Node.js	approveAll	(request, invocation) => PermissionRequestResult
Go	copilot.PermissionHandler.ApproveAll	PermissionHandlerFunc
.NET	PermissionHandler.ApproveAll	PermissionRequestHandler delegate
Python	PermissionHandler.approve_all	sync or async callable

Example (Go):

session, err := client.CreateSession(ctx, &copilot.SessionConfig{
    Model:               "gpt-5",
    OnPermissionRequest: copilot.PermissionHandler.ApproveAll, // or custom handler
})

// Custom: deny shell commands, approve everything else
OnPermissionRequest: func(req copilot.PermissionRequest, _ copilot.PermissionInvocation) (copilot.PermissionRequestResult, error) {
    if req.Kind == copilot.KindShell {
        return copilot.PermissionRequestResult{Kind: copilot.PermissionRequestResultKindDeniedInteractivelyByUser}, nil
    }
    return copilot.PermissionRequestResult{Kind: copilot.PermissionRequestResultKindApproved}, nil
},