Adds 'why does this job route here?' to the §7 scheduler:
- coordinator.explainJob() re-runs scoreCandidate against every live factory,
returning per-factory weighted breakdown, eligibility + reasons, deps state,
and the best eligible factory (read-only, side-effect free)
- GET /fleet/jobs/:id/explain route (404 when job missing)
- fleet-client.getJobExplain() + JobExplain/ScoreBreakdown types
- ExplainPanel on the job detail page: score table per factory with the six
weighted terms, eligibility, and unmet-deps note; degrades gracefully
- Tests: +2 coordinator, +1 routes, +2 fleet-client (fleet 144 green,
tracker-web 214 green)
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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