feat: add bun-fullstack agent and update skills

.agent/skills/tech-stack/elysiajs/plugins/opentelemetry.md

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+# OpenTelemetry Plugin - SKILLS.md
+
+## Installation
+```bash
+bun add @elysiajs/opentelemetry
+```
+
+## Basic Usage
+```typescript
+import { opentelemetry } from '@elysiajs/opentelemetry'
+import { BatchSpanProcessor } from '@opentelemetry/sdk-trace-node'
+import { OTLPTraceExporter } from '@opentelemetry/exporter-trace-otlp-proto'
+
+new Elysia()
+  .use(opentelemetry({
+    spanProcessors: [
+      new BatchSpanProcessor(new OTLPTraceExporter())
+    ]
+  }))
+```
+
+Auto-collects spans from OpenTelemetry-compatible libraries. Parent/child spans applied automatically.
+
+## Config
+Extends OpenTelemetry SDK params:
+
+- `autoDetectResources` (true) - Auto-detect from env
+- `contextManager` (AsyncHooksContextManager) - Custom context
+- `textMapPropagator` (CompositePropagator) - W3C Trace + Baggage
+- `metricReader` - For MeterProvider
+- `views` - Histogram bucket config
+- `instrumentations` (getNodeAutoInstrumentations()) - Metapackage or individual
+- `resource` - Custom resource
+- `resourceDetectors` ([envDetector, processDetector, hostDetector]) - Auto-detect needs `autoDetectResources: true`
+- `sampler` - Custom sampler (default: sample all)
+- `serviceName` - Namespace identifier
+- `spanProcessors` - Array for tracer provider
+- `traceExporter` - Auto-setup OTLP/http/protobuf with BatchSpanProcessor if not set
+- `spanLimits` - Tracing params
+
+### Resource Detectors via Env
+```bash
+export OTEL_NODE_RESOURCE_DETECTORS="env,host"
+# Options: env, host, os, process, serviceinstance, all, none
+```
+
+## Export to Backends
+Example - Axiom:
+```typescript
+.use(opentelemetry({
+  spanProcessors: [
+    new BatchSpanProcessor(
+      new OTLPTraceExporter({
+        url: 'https://api.axiom.co/v1/traces',
+        headers: {
+          Authorization: `Bearer ${Bun.env.AXIOM_TOKEN}`,
+          'X-Axiom-Dataset': Bun.env.AXIOM_DATASET
+        }
+      })
+    )
+  ]
+}))
+```
+
+## OpenTelemetry SDK
+Use SDK normally - runs under Elysia's request span, auto-appears in trace.
+
+## Record Utility
+Equivalent to `startActiveSpan` - auto-closes + captures exceptions:
+```typescript
+import { record } from '@elysiajs/opentelemetry'
+
+.get('', () => {
+  return record('database.query', () => {
+    return db.query('SELECT * FROM users')
+  })
+})
+```
+
+Label for code shown in trace.
+
+## Function Naming
+Elysia reads function names as span names:
+```typescript
+// ⚠️ Anonymous span
+.derive(async ({ cookie: { session } }) => {
+  return { user: await getProfile(session) }
+})
+
+// ✅ Named span: "getProfile"
+.derive(async function getProfile({ cookie: { session } }) {
+  return { user: await getProfile(session) }
+})
+```
+
+## getCurrentSpan
+Get current span outside handler (via AsyncLocalStorage):
+```typescript
+import { getCurrentSpan } from '@elysiajs/opentelemetry'
+
+function utility() {
+  const span = getCurrentSpan()
+  span.setAttributes({ 'custom.attribute': 'value' })
+}
+```
+
+## setAttributes
+Sugar for `getCurrentSpan().setAttributes`:
+```typescript
+import { setAttributes } from '@elysiajs/opentelemetry'
+
+function utility() {
+  setAttributes({ 'custom.attribute': 'value' })
+}
+```
+
+## Instrumentations (Advanced)
+SDK must run before importing instrumented module.
+
+### Setup
+1. Separate file:
+```typescript
+// src/instrumentation.ts
+import { opentelemetry } from '@elysiajs/opentelemetry'
+import { PgInstrumentation } from '@opentelemetry/instrumentation-pg'
+
+export const instrumentation = opentelemetry({
+  instrumentations: [new PgInstrumentation()]
+})
+```
+
+2. Apply:
+```typescript
+// src/index.ts
+import { instrumentation } from './instrumentation'
+new Elysia().use(instrumentation).listen(3000)
+```
+
+3. Preload:
+```toml
+# bunfig.toml
+preload = ["./src/instrumentation.ts"]
+```
+
+### Production Deployment (Advanced)
+OpenTelemetry monkey-patches `node_modules`. Exclude instrumented libs from bundling:
+```bash
+bun build --compile --external pg --outfile server src/index.ts
+```
+
+Package.json:
+```json
+{
+  "dependencies": { "pg": "^8.15.6" },
+  "devDependencies": {
+    "@elysiajs/opentelemetry": "^1.2.0",
+    "@opentelemetry/instrumentation-pg": "^0.52.0"
+  }
+}
+```
+
+Production install:
+```bash
+bun install --production
+```
+
+Keeps `node_modules` with instrumented libs at runtime.