fix(transcript-server): normalize Accept header for lenient MCP compatibility

[ochafik]

Problem

The MCP SDK's StreamableHTTPServerTransport returns 406 Not Acceptable when clients send:

• Accept: */*
• No Accept header

This happens because:

1. The SDK uses @hono/node-server to convert Node.js requests to Web Standard Requests
2. @hono/node-server reads from req.rawHeaders (immutable array), not req.headers
3. Simply modifying req.headers.accept in middleware doesn't affect the SDK's header check

Solution

Patch rawHeaders using Object.defineProperty() to normalize the Accept header before the SDK processes the request.

Changes

• Add normalizeAcceptHeader middleware that patches both req.headers and rawHeaders
• Add HTTP logging middleware for debugging (with request correlation IDs)
• Use app.post() with explicit 405 handlers for GET/DELETE (per SDK examples)

Testing

# All three now return 200:
curl -X POST http://localhost:5015/mcp -H 'Accept: application/json, text/event-stream' ...
curl -X POST http://localhost:5015/mcp -H 'Accept: */*' ...
curl -X POST http://localhost:5015/mcp ...  # no Accept header

Next Steps

Will copy main.ts to other example servers that use the same pattern.

[pkg-pr-new]

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commit: 3c1cc34