feat(tui-go): grant scope picker (A) + standing-grants viewer

Surface the new cross-session grant scopes in the TUI.

- Approve-always (A) now opens a scope picker instead of immediately
  creating a SESSION grant: choose this session / this project / everywhere.
  SESSION stays the default (A then enter/s = old behaviour); p and g
  create PROJECT / GLOBAL grants. The grant + approval are sent on confirm
  (esc cancels, leaving the call pending).
- New "grants" palette command + G shortcut open a standing-grants viewer
  (OverlayGrants) listing the active PROJECT/GLOBAL grants — scope, tool,
  permitted tiers, project path — with x/enter to revoke. The server's
  RevokeGrant reply (a fresh grant.list) refreshes it in place.
- protocol.go: TypeGrantList + GrantDto; RevokeGrant/ListGrants encoders;
  CreateGrant now documents the wider scopes. server.go decodes grant.list
  into m.grants and treats it as a non-session global reply.
- render-matrix coverage: grant.list classified as a non-rendering query
  reply (populates the overlay, not the transcript).
- demo.go: grants + grant-scope preview kinds.

go build / vet / test green; rendered both overlays via cmd/preview.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/tui-go/internal/app/model.go

@@ -59,6 +59,8 @@ const (
 	OverlaySessions
 	OverlayFiles
 	OverlayStatusbar
+	OverlayGrants
+	OverlayGrantScope
 )
 
 // RouterEntry is one line in a session's conversation transcript.
@@ -320,6 +322,15 @@ type Model struct {
 	sbHidden map[string]bool
 	sbIndex  int
 
+	// standing grants (OverlayGrants) — active PROJECT/GLOBAL grants from the grant.list reply.
+	grants        []protocol.GrantDto
+	grantsLoading bool
+	grantIndex    int
+	// grant scope picker (OverlayGrantScope) — chosen when the operator presses A on an approval.
+	// grantScopeIndex selects session/project/global; grantFor holds the approval being widened.
+	grantScopeIndex int
+	grantFor        *Approval
+
 	// animation
 	frame   int  // tick counter; drives spinner + caret blink
 	ticking bool // true while a tick loop is scheduled. The loop is gated on animating()