Achieve parity for OTel samples in all languages

[ceciliaavila]

Description

Analysis of the three OpenTelemetry samples to align them on features, style, README structure, and consistency.

Feature	.NET	Python	Node.js
Use case	Echo agent + OTel	Echo agent + OTel	Echo agent + OTel
Welcome message	"Hello and Welcome!"	"Welcome to the empty agent! …" ⚠️	"Hello and Welcome!" ✅
Echo message	"You said: {text}" ✅	"you said: {text}" ⚠️ lowercase	"You said now: {text}" ⚠️ extra "now"
Error handler	(implicit)	Explicit @on_error	(implicit)
Outbound HTTP call demo	❌	❌	✅ (fetch bing.com)
Custom spans in handlers	❌	❌	✅
Custom span events	❌	❌	✅
Custom metrics (counter/histogram)	❌	❌	✅
Traces	ASP.NET Core + HttpClient + Agents SDK	aiohttp server + client + requests	NodeSDK (no explicit auto-instrumentation)
Metrics	ASP.NET Core + HttpClient + runtime + Agents SDK	PeriodicExportingMetricReader	PeriodicExportingMetricReader
Logs	ILogger → OTLP	Python logging → OTLP	BatchLogRecordProcessor → OTLP
Span processor	Batch ✅	Simple ⚠️	Batch ✅
Agents SDK telemetry source	✅	❌	❌
Console fallback (no endpoint)	❌	❌	✅
Azure Monitor support	✅ (commented block)	❌	❌
Auth approach	Custom in-sample (~270 lines) ⚠️	SDK middleware (1 line) ✅	SDK built-in (0 lines) ✅
Auth disabled for local dev	✅	❓	❓
Gov cloud support	✅	❓ (SDK)	❓ (SDK)
JWT Token Validation in README	✅	❌	❌
env.TEMPLATE / config file	appsettings.json	env.TEMPLATE ⚠️ (incomplete)	env.TEMPLATE ✅
OTLP endpoint configurable	✅	✅ (missing from template ⚠️)	✅
Metrics/logs export interval config	❌	❌	✅
Service name	AgentsTelemetry.SourceName (SDK)	"otel_quickstart_agent" (hardcoded)	"OTelAgent" (hardcoded)
Dashboard setup	Docker in README	start_dashboard.ps1 script	Docker in README
Dashboard version pinned	latest	latest	9.2 (pinned) ⚠️
Dev tunnel instructions	✅	✅	❌
Agents Playground instructions	❌	❌	✅
WebChat access instructions	✅	✅	❌
"Viewing Telemetry" section in README	❌	❌	✅
OTel signals table in README	✅	✅	❌
Azure Monitor section in README	✅	❌	❌
Deploy to Azure instructions	✅	❌	❌
Separate server entry point	✅ Program.cs	✅ main.py	❌ (mixed in agent.ts)