Make access gating a first-class, pip-consumable extension point so a
consuming app can gate any of its own views behind 2FA / ALTCHA /
entitlement / feature flag / permission, or gate nothing, without editing
the kit.
- infrasynth.gates: Gate, GateResult, GatePermission, @gated and built-ins
TwoFactorGate, AltchaGate, EntitlementGate, FeatureGate, PermissionGate;
denials raise the correct namespaced error/status (per-endpoint, opt-in,
default is no gating)
- mint a `2fa` JWT claim only after verification (preserved across workspace
selection) so TwoFactorGate is meaningful for API/multi-workspace clients
- GatePermission added to DEFAULT_PERMISSION_CLASSES; HybridPermission
evaluates declared gates so kit permissions gate automatically
- document the extension surface and stable import paths in README