PR X: E2E round-trip against public Chain 138 RPC

Closes the CurrenciCombo side of proxmox blocker EXT-CHAIN138-CI-RPC
now that https://rpc.public-0138.defi-oracle.io is live (verified:
eth_chainId -> 0x8a / 138, eth_blockNumber returns a plausible
positive height).

Adds orchestrator/tests/e2e/notaryChainPublicRpc.e2e.test.ts -- a
**read-only** E2E suite that targets the real public Chain 138 RPC
instead of a locally-spawned ganache. We don't own a funded key on
Chain 138 in CI and writing against mainnet-equivalent infra would
be reckless, so the suite sticks to non-destructive calls:

  1. provider.getNetwork() returns a descriptor
  2. eth_chainId == 138
  3. eth_blockNumber > 0
  4. eth_getBlockByNumber returns a well-formed block with
     timestamp past 2020-09-13
  5. plans(bytes32) call against NOTARY_REGISTRY_ADDRESS (if set)
     returns a zero'd record for a synthetic key -- proves the ABI
     matches the deployed contract without mutating state
  6. orchestrator's services/notaryChain.ts gracefully mock-falls-
     back when the public RPC is configured but no signing key is
     set

Gated on BOTH RUN_E2E=1 AND E2E_USE_PUBLIC_CHAIN138=1 so the default
E2E path stays offline (existing ganache-based round-trip tests
don't need network).

CI: the orchestrator-e2e job now runs with E2E_USE_PUBLIC_CHAIN138=1,
so the 'run-e2e' PR label triggers **both** the Postgres
Testcontainers suite and the public Chain 138 suite.

Verification: RUN_E2E=1 E2E_USE_PUBLIC_CHAIN138=1 npx jest
--config=jest.e2e.config.js tests/e2e/notaryChainPublicRpc.e2e.test.ts
-> 6/6 passing, ~3s wall-clock. tsc --noEmit clean. No UI.

.github/workflows/ci.yml

@@ -146,8 +146,16 @@ jobs:
       - name: Install dependencies
         working-directory: orchestrator
         run: npm ci
-      - name: E2E tests (Testcontainers Postgres)
+      - name: E2E tests (Testcontainers Postgres + public Chain 138 RPC)
         working-directory: orchestrator
+        # EXT-CHAIN138-CI-RPC resolved via the public endpoint at
+        # https://rpc.public-0138.defi-oracle.io — the read-only
+        # public-RPC suite exercises the orchestrator's ethers client
+        # against a real Chain 138 node alongside the ganache-based
+        # round-trip tests. The env var opts the public-RPC suite in;
+        # without it, those tests self-skip.
+        env:
+          E2E_USE_PUBLIC_CHAIN138: "1"
         run: npm run test:e2e
 
   # Smart Contracts CI