[Core] Model Alfred node health states

[pallasathena92]

Summary

• replace Alfred's node-health booleans with one structured snapshot observation
• reconstruct Clear, Suspect, Unknown, and Unhealthy from configured Node conditions using one snapshot timestamp
• retain configured condition status and transition time with fail-closed precedence
• exclude every non-clear state from defrag targets and observed surge headroom
• wire hot-reloaded trigger conditions and recovery-suspicion windows into snapshot construction
• update OEP-0008 to distinguish recovery quarantine from future evacuation behavior

Safety boundary

This is the observation and target-safety foundation for Node-Health Policy #2. It does not generate evacuation candidates or remediation signals, dispatch migrations, write Nodes, change the workload package, or create a migration package.

Stacked on #828 (alfred/node-health-refresh).

Verification

• go test ./pkg/alfred/... ./cmd/alfred/... -count=1
• go test -race ./pkg/alfred/snapshot ./pkg/alfred/observer ./pkg/alfred/policy/defrag ./pkg/alfred/testutil -count=1
• go vet ./pkg/alfred/... ./cmd/alfred/...
• repository-wide pre-commit hooks

Summary by CodeRabbit

• New Features

  • Added structured node-health states: clear, suspect, unknown, and unhealthy.
  • Added recovery-based suspicion windows for temporarily failed conditions.
  • Non-clear nodes are quarantined from placement and surge-headroom calculations.
  • Only unhealthy nodes qualify for evacuation.
  • Added configurable node suspicion-window support with a default value.

• Bug Fixes

  • Node health evaluations now use consistent timestamps and condition severity.
  • Invalid or missing transition times fail closed as unknown.

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📝 Walkthrough

Walkthrough

The change replaces legacy node health flags with structured health observations. Snapshot building reconstructs health from configured conditions and transition times. Suspect, unknown, and unhealthy nodes are quarantined from placement and surge-headroom calculations.

Changes

Node health quarantine

Layer / File(s)	Summary
Structured health model and evaluation pkg/alfred/snapshot/types.go, pkg/alfred/snapshot/node_health.go, pkg/alfred/testutil/*	Node health now uses clear, suspect, unknown, and unhealthy states with condition observations and suspicion deadlines. Evaluation applies condition precedence, timestamp rules, deterministic ordering, and quarantine status.
Snapshot and refresh wiring pkg/alfred/snapshot/builder.go, pkg/alfred/snapshot/builder_test.go, pkg/alfred/config/config.go, pkg/alfred/observer/*	Snapshot construction receives the suspicion window and uses one timestamp for all node evaluations. Refresh passes the configuration through and excludes quarantined nodes from surge-headroom publication.
Placement quarantine and policy documentation pkg/alfred/policy/defrag/*, oeps/0008-alfred-gpu-cluster-caretaker/README.md	Defragmentation excludes quarantined health states. The OEP documents recovery-based suspicion, target quarantine, and the deferred evacuation behavior.

Estimated code review effort: 4 (Complex) | ~45 minutes

Merge Risk: 🔵 Low · up to ac82c

Composed test fixtures can represent an invalid unhealthy health observation, which can make health-policy tests validate behavior against impossible input. Reset the observation when constructing unhealthy fixtures before merge.

Sequence Diagram(s)

sequenceDiagram
  participant ObserverRefresh
  participant SnapshotBuild
  participant NodeHealthEvaluator
  participant PlacementPolicies
  ObserverRefresh->>SnapshotBuild: pass trigger conditions and suspicion window
  SnapshotBuild->>NodeHealthEvaluator: evaluate node conditions at one timestamp
  NodeHealthEvaluator-->>SnapshotBuild: return structured health state
  SnapshotBuild-->>ObserverRefresh: return node snapshot
  ObserverRefresh->>PlacementPolicies: provide snapshot for placement and headroom
  PlacementPolicies->>PlacementPolicies: exclude quarantined nodes

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🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 34.78% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 23 functions across 12 files. (1 skipped:…	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the primary change: introducing structured Alfred node health states.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

Docstring coverage is 34.78% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 23 functions across 12 files. (1 skipped: 1 unsupported.)

✨ Finishing Touches 💡 1

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• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch alfred/node-health-state

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Actionable comments posted: 1

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Inline comments:
In `@pkg/alfred/testutil/builder.go`:
- Line 57: Update NodeUnhealthy to replace Node.Health with a fresh
NodeHealthObservation configured as NodeHealthUnhealthy, rather than mutating
only State and retaining SuspectUntil. Add a regression test composing
NodeSuspect() followed by NodeUnhealthy() and assert the resulting SuspectUntil
is nil.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

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Run ID: 48610fec-b321-45dd-867d-b447c58ede2a

📥 Commits

Reviewing files that changed from the base of the PR and between 819f2ce and ac82c29.

📒 Files selected for processing (13)

• oeps/0008-alfred-gpu-cluster-caretaker/README.md
• pkg/alfred/config/config.go
• pkg/alfred/observer/loop.go
• pkg/alfred/observer/loop_test.go
• pkg/alfred/policy/defrag/scoring.go
• pkg/alfred/policy/defrag/scoring_test.go
• pkg/alfred/snapshot/builder.go
• pkg/alfred/snapshot/builder_test.go
• pkg/alfred/snapshot/node_health.go
• pkg/alfred/snapshot/node_health_test.go
• pkg/alfred/snapshot/types.go
• pkg/alfred/testutil/builder.go
• pkg/alfred/testutil/builder_test.go

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