P6: S3 blob store, Helm chart, air-gapped installer verify loop

- S3BlobStore (object_store, path-style) behind the same BlobStore trait,
  tested against a REAL MinIO container (round trip, overwrite, NotFound
  on get and delete, nested keys); [storage] backend=local|s3 config with
  validation + server-side selection (S3 creds via env overlay)
- Helm chart: server pod with the secret broker as a SIDECAR sharing a
  private emptyDir unix socket (no network hop carries credentials),
  frontend, optional local PVC vs S3, OIDC/oauth values, unbuffered-SSE
  ingress annotations, NetworkPolicies (frontend->server only), hardened
  securityContexts; ci/check-helm.sh lints AND asserts the rendered
  topology properties
- deploy/airgapped/install.sh: offline signature+checksum verification via
  the bundled teamclaw-bundler BEFORE any docker load; --verify-only mode;
  ci/test-install.sh rehearses clean/tampered/wrong-key paths with the
  real binary
- CI: helm gate + installer rehearsal wired in

149 Rust tests; helm lint + rendered assertions green; installer
verify-path rehearsal green.

Co-Authored-By: Claude Fable 5 <[email protected]>

crates/tc-config/tests/config.rs

@@ -139,3 +139,15 @@ fn missing_file_is_a_clear_error() {
         Ok(())
     });
 }
+
+#[test]
+fn s3_backend_requires_endpoint_and_bucket() {
+    figment::Jail::expect_with(|jail| {
+        let toml =
+            format!("{AIR_GAPPED_TOML}\n[storage]\ndata_dir = \"./data\"\nbackend = \"s3\"\n");
+        jail.create_file("teamclaw.toml", &toml)?;
+        let err = AppConfig::load_from(&jail.directory().join("teamclaw.toml")).unwrap_err();
+        assert!(matches!(err, ConfigError::Invalid(msg) if msg.contains("s3_endpoint")));
+        Ok(())
+    });
+}