[codex] add query log resource usage fields

[bill-ph]

Summary

• add cpu_time_s and peak_buffer_memory_bytes to system.query_log
• populate both fields from the existing DuckDB profiling summary path alongside postgres_scan_ms
• add query-log defaults/backfill so unavailable profiling stores 0, not NULL
• emit duckdb.cpu_time_s on execute spans and document the new query-log fields

Scope

This intentionally follows the existing postgres_scan_ms convention. It does not expand profiling coverage for COPY, simple-batch, or other paths that were not already reliably covered by the existing profiling summary flow.

Validation

• go test ./server -run 'TestEnsureQueryLogTable(CreatesResourceUsageColumns|AddsOrgIDToExistingTable)|Test(QueryLoggerFlushBatchPersistsOrgID|LogQueryCopiesProfilingSummaryToQueryLogEntry|EnrichSpanWithProfilingSummaryIncludesResourceUsage)'
• go test ./server
• go test ./server/observe ./server/flightclient
• just test-unit
• just lint
• git diff --check