feat(mcp-transport): add Effect.fn + OTEL instrumentation

Convert MCP transport from plain async/await to Effect services with
automatic OTEL span creation. Extract duplicated callApi logic (~200
lines) from both entry points into shared api-fetch.ts module.

New services: MCPTracingService, MCPLoggerService, MCPCacheService,
MCPApiService (with Effect.withSpan), otel-init (NodeSDK), layers.

Each tool handler gets an Effect.fn export (searchPatternsEffect, etc.)
alongside the existing async wrapper for backward compatibility.
All 231 existing tests pass unchanged; 11 new service tests added.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: PaulJPhilp

bun.lock

@@ -33,7 +33,16 @@
     "typecheck": "tsc --noEmit"
   },
   "dependencies": {
+    "@effect/opentelemetry": "^0.61.0",
     "@modelcontextprotocol/sdk": "^1.25.2",
+    "@opentelemetry/api": "^1.9.0",
+    "@opentelemetry/exporter-trace-otlp-http": "^0.212.0",
+    "@opentelemetry/resources": "^2.2.0",
+    "@opentelemetry/sdk-node": "^0.212.0",
+    "@opentelemetry/sdk-trace-base": "^2.0.0",
+    "@opentelemetry/sdk-trace-node": "^2.2.0",
+    "@opentelemetry/semantic-conventions": "^1.38.0",
+    "effect": "3.19.19",
     "zod": "^4.3.6"
   },
   "devDependencies": {