trim: remove dead code and move large spec docs to attic

- Remove unused exports: renderProgress, formatTripleBoundaryCounterexample, clearCapturedRoutes
- Remove dead BUILTIN_PLUGIN_CONTRACTS constant (auto-registration removed earlier)
- Fix app-loader error messages to mention multiple export patterns
- Move to attic: protocol-extensions-spec, OUTBOUND_CONTRACT_MOCKING_SPEC, PLUGIN_CONTRACTS_SPEC, fastify-structure
- Build: clean | Tests: 849 pass, 0 fail

src/domain/plugin-contracts.ts

@@ -143,46 +143,6 @@ export class PluginContractRegistry {
   }
 }
 // ============================================================================
-// Built-in Plugin Contracts
-// ============================================================================
-export const BUILTIN_PLUGIN_CONTRACTS: Record<string, PluginContractSpec> = {
-  '@fastify/auth': {
-    appliesTo: '**',
-    hooks: {
-      onRequest: {
-        requires: ['request_headers(this).authorization != null'],
-      },
-    },
-  },
-  '@fastify/compress': {
-    appliesTo: '**',
-    hooks: {
-      onSend: {
-        ensures: ['response_headers(this).content-encoding != null'],
-      },
-    },
-  },
-  '@fastify/cors': {
-    appliesTo: '**',
-    hooks: {
-      onRequest: {
-        ensures: ['response_headers(this).access-control-allow-origin != null'],
-      },
-    },
-  },
-  '@fastify/rate-limit': {
-    appliesTo: '**',
-    hooks: {
-      onRequest: {
-        ensures: [
-          'response_headers(this).x-ratelimit-limit != null',
-          'response_headers(this).x-ratelimit-remaining != null',
-        ],
-      },
-    },
-  },
-}
-// ============================================================================
 // Factory
 // ============================================================================
 export function createPluginContractRegistry(): PluginContractRegistry {