fix(P04): wire ACL enforcement + WebAuthn reg auth + audit actor (REQ-153)

R-023: Zero-trust enforcement operationally wired.

ACL enforcement (C-45 staged rollout):
- acl.Check wired into all 5 daemon handlers (dispatch/jobs/nodes/tasks)
- health endpoints exempt (liveness probes not gated)
- ACL log-only mode default (config acl.enforce=false); enforce after
  bootstrap ACL verified
- sshpush auth: ORCA_OIDC_TOKEN validated against JWKS before apply
- txn apply: Authorize hook validates OIDC token before running pull
- acl.json mode 0600 (was 0644)
- flock on acl.json for concurrent grant/revoke
- bootstrap ACL: init grants cluster-admin to orca-admins group + SVID

Audit actor identity:
- currentActor reads OIDC sub from credentials.json (was hardcoded "cli")
- threaded through all audit.Record calls via context

WebAuthn registration auth:
- BeginRegistration/FinishRegistration require authenticated session
- fail-closed 401 when no authFunc configured

New files: internal/daemon/acl.go, internal/cli/authactor.go,
internal/engine/actor.go, internal/identity/authtoken.go,
internal/sshpush/auth.go, internal/txn/auth_test.go

---ci---
project: orca
phase: 4
milestone: v0.13
status: complete
requirements:
  covered: [153]
---/ci---

internal/cli/node.go

@@ -408,7 +408,7 @@ LOCAL ONLY (D-046): does not touch the remote host's authorized_keys.
 		if dbErr == nil {
 			defer dbCloser()
 			audit := engine.NewAudit(store.NewAuditRepo(db), newLogger())
-			audit.Record(ctx, "cli", "node.key_reset", node.ID, "success", nil, map[string]any{
+			audit.Record(ctx, actorFromCtx(ctx), "node.key_reset", node.ID, "success", nil, map[string]any{
 				"node": node.Name,
 				"host": host,
 			})