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/helm/cairnobs/README.md

@@ -99,7 +99,7 @@ unconditional by design, no disable switch.
 both tenants reached `status.phase: Active` with real credentials.
 
 This proves Phase 4's "two tenants... with their own users, roles,
-dashboards" exit criteria (`/CLAUDE.md`) end to end at the deployment-
+dashboards" exit criteria (`/PROJECT-SPEC.md`) end to end at the deployment-
 topology layer: `-provision-tenant` (`enterprise/internal/
 tenantprovision`) is what actually creates each tenant's ClickHouse
 database/user/grant and marks it active in `rbacstore`; running inside

deploy/helm/cairnobs/values.yaml

@@ -94,7 +94,7 @@ search:
   # A second replica would form a second, independent consumer instance
   # against the same partitions with no coordination -- correctness,
   # not just resource waste, is the reason this isn't a `replicas` knob
-  # yet. Matches CLAUDE.md's Phase 4 non-goal: "no general multi-cluster
+  # yet. Matches PROJECT-SPEC.md's Phase 4 non-goal: "no general multi-cluster
   # orchestration."
   replicas: 1
   resources: {}