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.

src/bootstrap/runtime-adapters.ts

@@ -505,6 +505,7 @@ export async function createRuntimeAdapters(
   });
   const featureInputs = createInstalledFeatureInputs({
     contractOperations,
+    studioSource: config.TECH_LOG_STUDIO_SOURCE,
   });
 
   return Object.freeze({

src/bootstrap/runtime-config-schema.ts

@@ -50,6 +50,12 @@ export type RuntimeConfig = Readonly<{
    * feature the build did not install cannot be named into existence here.
    */
   FEATURE_OVERRIDES: ProductFeatureOverrideMap;
+  /**
+   * §3.5-adjacent runtime switch: which Studio gateway adapter this build
+   * talks to. A V1 document predates the key and is always normalized to
+   * MOCK.
+   */
+  TECH_LOG_STUDIO_SOURCE: "MOCK" | "HTTP";
   /** Present only while a V1 document is still accepted. */
   LEGACY_API_CONTRACT_VERSION?: string;
 }>;
@@ -132,6 +138,11 @@ export function validateRuntimeConfig(value: unknown): RuntimeConfigValidation {
     FEATURE_OVERRIDES: Object.freeze({
       ...(isV2 ? (parsed as RuntimeConfigV2).FEATURE_OVERRIDES : {}),
     }),
+    // A V1 document predates the Studio adapter switch; it always normalizes
+    // to the mock so the backend-absent default holds for legacy documents.
+    TECH_LOG_STUDIO_SOURCE: isV2
+      ? (parsed as RuntimeConfigV2).TECH_LOG_STUDIO_SOURCE
+      : "MOCK",
     ...(isV2
       ? {}
       : {