Rename the project spec and update every reference to it

The charter file carried a tool-specific name while being the repository's own
document: mission, non-negotiable constraints, the pinned stack, repo
conventions and phase status, cited as authority by thirty files across the
agent, api, deploy, docs, search and terraform trees.

PROJECT-SPEC.md says what it is. All 42 references are updated in the same
commit, including the relative link in docs/status.md, so nothing points at a
filename that no longer exists.

enterprise/internal/tenantcrd/tenantcrd.go

@@ -1,6 +1,6 @@
 // Package tenantcrd syncs enterprise-api -provision-tenant's real
 // provisioning result into the Tenant CRD (deploy/operator/api/
-// v1alpha1) -- the "lightweight unification" named in CLAUDE.md's "two
+// v1alpha1) -- the "lightweight unification" named in PROJECT-SPEC.md's "two
 // independent provisioning mechanisms" gap: -provision-tenant stays the
 // sole real actor (rbacstore + tenantprovision.ProvisionClickHouse, see
 // runProvisionTenant's doc comment in cmd/enterprise-api/main.go); this