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.

deploy/operator/api/v1alpha1/tenant_types.go

@@ -18,7 +18,7 @@ import (
 // internal/controller/tenant_controller.go's doc comment for how
 // TenantReconciler derives Phase/Conditions from those fields rather
 // than fabricating its own "provisioned" claim. This is the "lightweight
-// unification" named in CLAUDE.md/docs/phase-4-runbook.md's "two
+// unification" named in PROJECT-SPEC.md/docs/phase-4-runbook.md's "two
 // independent provisioning mechanisms" gap: -provision-tenant stays the
 // real actor; this operator's reconcile loop never touches Postgres or
 // ClickHouse and gained no new credentials.