feat: select the TechLog Studio adapter from runtime configuration

Adds TECH_LOG_STUDIO_SOURCE (MOCK | HTTP, default MOCK) to the V2 runtime
config schema so a build can switch createTechLogFeatureInstalledInput
between the mock and HTTP Studio gateways without a rebuild. V1 documents
predate the key and always normalize to MOCK. The HTTP gateway is
constructed with only { operations } per Task 4's actual signature -
no CSRF provider is wired here; that lands with attachCredentials at a
later composition-root task.

Updates every existing Studio test call site to the new required
createTechLogFeatureInstalledInput(context) signature via a shared
tests/helpers/studio-install-context.ts MOCK fixture, so the whole
existing Studio suite keeps exercising the mock adapter unchanged.

tests/helpers/studio-install-context.ts

@@ -0,0 +1,15 @@
+import type { TechLogInstallContext } from "../../src/features/tech-log/adapters/create-tech-log-feature-input.ts";
+
+/**
+ * The install context the existing Studio test suite composes against. It
+ * always selects the mock adapter, so `contractOperations` is a throwing stub
+ * — `createTechLogFeatureInstalledInput` never reads it on the MOCK branch.
+ */
+export const MOCK_STUDIO_INSTALL_CONTEXT: TechLogInstallContext = Object.freeze({
+  studioSource: "MOCK",
+  contractOperations: Object.freeze({
+    async execute() {
+      throw new Error("contract executor is not used by the mock Studio gateway");
+    },
+  }),
+});