feat(observability): OS signposts for pressure / pageout / freeze-tier

[froggychips]

Summary

Adds time-correlated signposts in three places that produce the clearest pressure → freeze decision → pageout outcome timeline in Instruments:

• MemoryPressureSource — signpost event on each level change (.normal / .warning / .critical), with PointsOfInterest twin so the standard PoI track shows pressure changes alongside any other component's events.
• PageoutChain.pageout — interval per strategy attempt, with strategy + outcome (success / skipped / failed). Closes the validation-gate question from ADR-0007 / 0011: "which pageout strategy actually fires on this machine".
• VortexCoordinator.freezeTier — interval per freeze cycle, with tier + candidate count + final frozen count.

Why

Today's live session showed the three biggest gaps in current observability:

1. We could not tell from the unified log alone whether mach_vm_behavior_set was actually fired or skipped under fallback to jetsam.
2. We could not see the latency between a .warning dispatch event and the actual freezeTier call.
3. We had no time-correlated picture of pressure level vs freeze decisions vs pageout outcomes.

All three are now visible as a single Instruments timeline.

How to use

xcrun instruments -t Logging /path/to/.build/release/FroggyDaemon
# or
open /Applications/Xcode.app/Contents/Applications/Instruments.app
# Choose the "Logging" template, attach to FroggyDaemon, filter
# subsystem == com.froggychips.froggy

Behavior change

None. Existing os.Logger lines preserved. Signposts are observability-only.

Test plan

• make build clean
• Manual: run daemon, push pressure to .warning and .critical, verify Instruments shows correlated pressure-level events + freeze-tier intervals + pageout-attempt intervals
• Verify no regressions in existing tests (make test)

Follow-ups (not in this PR)

• ADR for "Observability via OS signposts" recording categories + intent
• Signposts for VortexActor.thawProcess / thawAll (thaw timeline)
• Signposts for VisionActor OCR cycles
• Signposts for full generation pipeline in MLXSupervisor (partial coverage exists)

Related

• ADR-0006 reactive memory pressure
• ADR-0007 pageout strategies
• ADR-0011 validation gate (substrate-level honesty)
• ADR-0014 design docs after implementation

[froggychips]

Ветка пересажена на текущий main (ce85f22) — прежняя история разошлась с main ещё в мае (общий предок f46d9c9), поэтому вместо мержа сделан cherry-pick содержательного коммита и force-push.

Что изменилось при пересадке: MemoryPressureSource и PageoutChain легли без правок, а вот freezeTier с мая переписан (обход per-bundleId, audit log, frontmost-veto, inFlightFreezes, проверки поколения политики), поэтому interval пришлось переложить на нынешний обход: candidates считается по ходу, frozen — только реально вставленные в tier-set, в метке добавлен reason. Поведение не меняется.

Проверка: swift build для FroggyDaemon / froggy / FroggyAudioWorker проходит без ошибок и без новых предупреждений. Тесты не запускались — на машине нет Xcode (только CommandLineTools, import XCTest не резолвится), self-hosted раннер offline.

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Breezy!

Reviewed commit: 2dbaefbb09

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