Add gateway.jsonl parsing for MCP server usage metrics

[Copilot]

The MCP gateway container logs server and tool usage to gateway.jsonl in JSONL format, but the logs and audit commands couldn't parse this data to show usage metrics.

Changes

New gateway log parser (pkg/cli/gateway_logs.go)

• Parses JSONL format with entries like:

  {"timestamp":"2024-01-12T10:00:00Z","event":"tool_call","server_name":"github","tool_name":"get_repository","duration":150.5,"status":"success"}

• Aggregates per-server metrics: request counts, tool calls, durations, errors
• Aggregates per-tool metrics: call counts, avg/max/min durations, input/output sizes
• Combines metrics across multiple workflow runs

Display integration

• gh aw logs: Shows aggregated gateway metrics after main output
• gh aw audit: Shows gateway metrics after audit report
• Verbose mode includes detailed tool breakdowns per server
• Gracefully skips runs without gateway.jsonl (normal for non-gateway workflows)

Example output

MCP Gateway Metrics

Total Requests: 6
Total Tool Calls: 6
Total Errors: 1
Servers: 2

Server Usage:
┌────────────────────────────┬──────────┬────────────┬───────────┬────────┐
│ Server                     │ Requests │ Tool Calls │ Avg Time  │ Errors │
├────────────────────────────┼──────────┼────────────┼───────────┼────────┤
│ github                     │        4 │          4 │    158ms  │      1 │
│ playwright                 │        2 │          2 │    400ms  │      0 │
└────────────────────────────┴──────────┴────────────┴───────────┴────────┘

Testing

• 13 test functions covering valid logs, errors, multiple servers, invalid JSON, aggregation
• All tests passing, linting clean

Original prompt

Make sure the download logs function in .go is able to parse the gateway.jsonl file.

When it finds it, it should gather basic usage metrics of the servers and tools, from the JSONL messages.

Display a table with the results in logs and audit.

See recent runs of smoke-Claude for gateway.log file

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