Add query log e2e smoke and runbook

[bill-ph]

Summary

• add an mw-dev e2e smoke that verifies successful and failed marker queries land in ducklake.system.query_log
• assert cpu_time_s and peak_buffer_memory_bytes are present/non-negative for completed query-log rows
• add a query-log writer operator runbook and static guard tests for the harness/docs

Review fixes already applied

• made the static harness guard independent of whitespace alignment
• corrected the runbook producer-mode check for valueFrom ConfigMap refs
• corrected writer metric names to outcome=inserted/committed

Tests

• go test ./tests/manifests
• sh -n tests/e2e-mw-dev/harness.sh
• just test-unit
• 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	3	0
E2E/journey files	0	2	0
Workflow files	0	0	0

Signals

• Test cases: +3 / -0
• Assertions: +7 / -0
• 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: needs review

Warnings

• E2E or journey files changed (needs review)
  • tests/e2e-mw-dev/README.md
  • tests/e2e-mw-dev/harness.sh