Prototype: declarative TrackingReconcile pure core

[kyleve]

Prototype (draft) — stacked on #184

Exploratory follow-on to TLA+ protocol expansion for Where. Not merge-ready — validates whether extracting the tracking-toggle protocol into pure WhereCore functions makes the spec mapping easier to digest.

Hypothesis

The interesting parts of TrackingReconciliation are declarative (effective = desired ∧ auth, publish-at-quiescence, preempt-on-stop). They should live in testable pure functions, with async orchestration calling through.

What this adds

• TrackingReconcile — pure effective/publish/preempt decisions, doc-linked to TLA properties
• LocationIngestorStart — post-locationSource.start() branch
• Unit tests mirroring Coalesced.cfg scenarios (no Task / ingestor fakes)
• Thin wiring in WhereSession.trackingWorkerLoop and LocationIngestor.start()

Non-goals

• Generic coalescing worker abstraction
• Launch/handoff/scope protocols
• Full migration of every tracking entry point beyond current worker

Verification

• TrackingReconcileTests, LocationIngestorStartDecisionTests
• WhereSessionTrackingTests (including newerStopWinsOverInFlightStart)

Next step if this lands

Consider whether a shared coalescing-worker helper pulls its weight once a second protocol wants the same loop.