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/contracts/release-artifacts.ts

@@ -156,6 +156,9 @@ export const runtimeConfigV2ArtifactSchema = z
     CONFIG_SCHEMA_VERSION: z.literal("2.0"),
     CAPABILITY_OVERRIDES: capabilityOverrideArtifactSchema,
     FEATURE_OVERRIDES: featureOverrideArtifactSchema,
+    // TechLog Studio adapter selection. Backend is not live yet, so the
+    // default is the in-memory mock; a document may opt a build into HTTP.
+    TECH_LOG_STUDIO_SOURCE: z.enum(["MOCK", "HTTP"]).default("MOCK"),
   })
   .strict()
   .superRefine(runtimeConfigArtifactInvariants);