Add Dify, Exa, and n8n instrumentation examples

[Nightingalelyy]

Summary

• refresh Python Dify examples and add async plus Knowledge Base/Workspace coverage with released-SDK capability skips
• add TypeScript Dify loopback/live examples for chat, streaming, completion, workflows, knowledge, files, and controlled failures
• add Python and TypeScript Exa loopback/live suites for search, contents, grounded answers, streams, tools, Agent/Research, and expected failures
• add n8n 2.37.7 native OpenTelemetry fixtures for workflow/node success and failure plus deterministic Agent, LLM, tool, and memory spans

Validation

• Python Dify: run_all.py loopback suite with one shared run marker
• TypeScript Dify: npm run typecheck and npm run examples
• Python Exa: run_all.py loopback suite with one shared run marker
• TypeScript Exa: npm run typecheck and npm run all
• n8n: deterministic Agent fixture plus the real 2.37.7 OTLP/Protobuf success/failure path on Node 24
• scoped Respan trace trees/spans reviewed for hierarchy, content, failures, streaming completion, metadata, deduplication, and secret absence
• git diff --check passed; generated dependency trees, local credentials, and absolute developer paths are excluded

Dependency and ordering

• Depends on feat(instrumentation): refresh Dify and add Exa and n8n respan#400 for the instrumentation packages and runtime behavior exercised here
• Merge this example PR after the SDK PR so local checkout paths and source references resolve from upstream main
• Public documentation is prepared separately and intentionally remains outside this PR for follow-up review