Capture profiles from Flight DoGet

[bill-ph]

Summary

• capture DuckDB profiling only from the completed Flight DoGet execution
• consume the DoGet trailer after the Flight result stream reaches EOF
• defer query span and query-log enrichment until result streaming is complete
• represent DuckDB operator timing as cumulative attributes instead of a fabricated sequential timeline

Why

GetFlightInfo performs schema discovery, so its profile described the schema probe rather than the statement execution. The completed DoGet profile was never returned to the control plane.

Impact

Query traces and terminal query-log profile fields now describe the actual result-producing execution. Stale, canceled, and absent profile files are ignored.

Validation

• go test ./duckdbservice ./server/flightclient ./server ./server/observe
• just lint

[github-actions]

Test Impact Plan

Deterministic summary of how this PR changes tests, CI runners, and coverage-risk signals.

Summary

Area	Added	Changed	Deleted
Test files	0	4	0
E2E/journey files	0	0	0
Workflow files	0	0	0

Signals

• Test cases: +3 / -0
• Assertions: +14 / -1
• Skips or known failures added: 0
• Workflow continue-on-error added: 0
• Workflow path filters added: 0
• Test commands removed from justfile: 0
• E2E/journey retry lines added: 0

Coverage risk: neutral or increased

No coverage-reduction warnings detected.