FLEX-WP-0008 T01-T02: tenant-engine resource/action vocabulary + policy package

docs/tenant-engine-{resource-namespace,action-vocabulary}.md: four actions
(tenant.create, tenant.role.grant, tenant.role.revoke, tenant.plan.assign)
matching tenant_engine/src/tenant_engine/authz.py's _RESOURCE_TYPES mapping
exactly. No resource_manifest.yaml -- tenant-engine's resources are created
dynamically, unlike ops-warden's fixed SSH-certificate inventory; documented
as a deliberate deviation.

examples/tenant-engine/: protected_system_manifest.yaml, subject_manifest.yaml
(one registered caller: tenant-engine's own service identity),
policy_package.md (Rego rules + embedded tests), policy_fixtures.yaml (8
allow/deny pairs), assembled registry_snapshot.json, two standalone
check_request examples, README.

Design decision made explicit in the workplan: operator/service-identity
authorization (one known subject, four known actions), not aal2+assurance +
tenant-capability-role checking -- CheckRequest carries no assurance claim
yet (TEN-WP-0003 already flagged actor as a plain request-body field, not a
real auth context), and a tenant's capability roles are the tenant's own
state, not a property of who may call tenant-engine's admin API. Revisit
once KEY-WP-0005 gives callers a real assurance-bearing identity.

Verified for real: built ./cmd/flex-auth, ran test-policy (6 tests + 8
fixtures, all pass), load-registry, check against both example requests.
Then ran a live flex-auth serve with this exact registry+policy and pointed
tenant-engine's real, unmodified FlexAuthCheckClient/FlexAuthWriteAuthorizer
at it over real HTTP: unknown subject -> 403, tenant-engine -> 201. go test
./... still green across the whole repo.

T03 (live-lookup context adapter for other protected systems) stays open --
new Go adapter package, tracked separately.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

examples/tenant-engine/subject_manifest.yaml

@@ -0,0 +1,25 @@
+id: subjects:tenant-engine-operators
+tenants:
+  - id: tenant:platform
+    name: Platform Tenant
+subjects:
+  - id: tenant-engine
+    type: Service
+    display_name: tenant-engine service principal
+    organization_relation: ServiceProvider
+    roles:
+      - Operator
+    groups:
+      - group:tenant-engine-writers
+    tenant: tenant:platform
+    metadata:
+      description: >-
+        tenant-engine's own service identity, used for the tenant.create /
+        tenant.role.grant / tenant.role.revoke / tenant.plan.assign actions
+        it sends to POST /v1/check (authz.FlexAuthWriteAuthorizer).
+groups:
+  - id: group:tenant-engine-writers
+    display_name: tenant-engine Write API Callers
+    members:
+      - tenant-engine
+    tenant: tenant:platform