docs(v0.215.0): CHANGELOG, CONTEXT decisions, README feature, REUSE entries

- CHANGELOG leads with the severity fix and the live warning-vs-warn proof.
- CONTEXT records the settled decisions so they are not re-litigated: Hiba is
  the label for predicted failure (no fourth word); sustain before count and
  why; the provenance of 64/55/60; phase 2 owns the new SMART attributes
  because they are a wire change under G-1; phase 1 state is one record per
  disk, not a series.
- README documents the 14-row ladder, the persisted state, the hourly cadence
  and the five message shapes.
- REUSE pins the severity wire contract on PushEvent — the defect's real home,
  so the next typo'd severity is caught at the table rather than in production
  — and records priorFor vs cardPriorFor, which differ by one observation and
  make the chip disagree with the email if mixed up.

REUSE.md

@@ -159,15 +159,18 @@
 | `Client.AddNetStorage/ListNetStorage/RemoveNetStorage` | controller/internal/agentapi/client.go | NAS mounts (A1) | Network storage | Password passes through to agent's 0600 cred file; controller NEVER persists it |
 | `agentapi.StatusError` | controller/internal/agentapi/client.go | `{Path, Code}` typed non-2xx GET error | Distinguishing HTTP statuses from transport errors (`errors.As`) | NEVER string-match agent error text — the capability probe keys on `Code==404` |
 | `SupportCache.Supports` / `Client.Supports` | controller/internal/agentapi/features.go | `(ctx, prober, Feature) SupportState` | Agent-capability gate for COUPLED features (route probe, TTL 5m) | 404 ⇒ No; transport/5xx ⇒ Unknown (NEVER refuse on Unknown). New coupled feature = new `featureProbes` row + gate call at the entry point + `MinAgent:` in the CHANGELOG header (publish-train-rules.md). Web layer: `Server.netFeatures` through the `netAgent` seam |
-| `agentapi.DiskVerdictFor` / `DiskVerdict.Label` / `DegradedAttributes` | controller/internal/agentapi/diskverdict.go | `(*SmartSummary) DiskVerdict` | THE shared disk-health verdict (card chip + 6h check) — v0.169.0 | Pure; nil/UNKNOWN → `DiskVerdictUnknown` (Nincs adat, NEVER alarms); percentage_used threshold is **≥90**. Feature-detects the agent's `DiskInfo.Smart` (nil = old agent). Do NOT recompute the verdict inline anywhere |
+| `agentapi.DiskVerdictFor` / `DiskVerdict.Label` / `DegradedAttributes` / `UncorrectableSectors` / `DiskPrior` / `TemperatureFailC` | controller/internal/agentapi/diskverdict.go | `(*SmartSummary, DiskPrior) DiskVerdict` | THE shared disk-health verdict (card chip + hourly check) — v0.169.0, 14-row ladder v0.215.0 | Pure — no clock, no I/O; history arrives as `DiskPrior`. nil/UNKNOWN → `DiskVerdictUnknown` (Nincs adat, NEVER alarms, row 1 is first for that reason). **Never trust `smart_status.passed`**: attrs 187/197/198 carry `thresh: 0`, so it cannot fail on unreadable sectors. A zero `DiskPrior` is the fail-safe (first sighting can only reach Figyelmeztetés). **Four labels, no fifth** — predicted failure is „Hiba". Do NOT recompute the verdict inline anywhere, and do NOT re-literal 60 °C — use `TemperatureFailC` |
 | `Server.resolveBackupTargetState` / `backupTargetView` | controller/internal/web/backup_target_offer.go | `(ctx)` → state / `*BackupTargetView` (nil = render nothing) | The whole-system backup-target answer: healthy · degraded-never-configured · **TargetAbsent** (configured, drive gone) · unknown | Test seams `Server.tiersFn` + `Server.disksFn` (nil → the real client). **`degradedMessageFor` is the ONE place that decides customer copy** — add a state there, never in a template. `backupTargetView` returns **nil** for healthy AND unknown so a template typo cannot decorate a working box. R-112: this state had NO consumer for two releases; the render is server-side on `backups.html`, and the seam test drives `backupsHandler` and asserts rendered HTML |
-| `Server.cachedDisks` / `RunDiskHealthCheck` | controller/internal/web/disk_health.go | `(ctx)` | Card fetch (60s TTL) / the 6h degradation check | Card uses the 60s TTL cache (anti-smartctl-storm); the CHECK fetches FRESH (`fetchDisks`). Test seams: `Server.disksFn` (source) + `Server.diskNotifyFn` (sink). Baseline is in-memory (restart re-baselines) |
+| `Server.cachedDisks` / `RunDiskHealthCheck` | controller/internal/web/disk_health.go | `(ctx)` | Card fetch (60s TTL) / the hourly degradation check | Card uses the 60s TTL cache (anti-smartctl-storm); the CHECK fetches FRESH (`fetchDisks`). Test seams: `Server.disksFn` (source) + `Server.diskNotifyFn(notify.DiskAlert)` (sink). State is PERSISTED (v0.215.0) — a restart no longer re-baselines |
+| `diskAlertDecision` / `diskAlertKindFor` / `Server.priorFor` / `Server.cardPriorFor` | controller/internal/web/disk_health_state.go | pure + `(key) agentapi.DiskPrior` | Whether an observation emits, and which message shape | Compares against the **last ALERTED** verdict, not the last observed — that is what collapses a flap to one alert. Re-alert needs doubling **AND** 24h (an AND). **`priorFor` is for the CHECK, `cardPriorFor` for the CARD** — they differ by one observation and mixing them makes the chip read one level more severe than the email |
+| `diskRecord` / `writeDiskState` / `Server.loadDiskStateLocked` | controller/internal/web/disk_health_state.go | `disk-health-state.json` in `cfg.Paths.DataDir` | Persisted per-disk observation + alert history | Atomic tmp+rename (the `selfupdate.SaveState` shape, copied not imported). Missing file = normal; corrupt = LOG and fall back to no-prior, **never fatal**. Written ONCE per check run. Keyed by `diskKey`. **One record per disk, NOT a sample series** — history is Phase 2/3 in `metrics.MetricsStore` |
 
 ### Notifications / hub sync
 
 | Symbol | File | Short signature | Use for | Gotchas |
 |---|---|---|---|---|
-| `Notifier.PushEvent` | controller/internal/notify/notifier.go | `(eventType, severity, message, details)` | Hub events | Async goroutine, 3 attempts/3s backoff. NEW event types MUST be added to hub `allowedEventTypes` or POST /event 400s; hub only emails `warning`/`error` from this path |
+| `Notifier.PushEvent` | controller/internal/notify/notifier.go | `(eventType, severity, message, details)` | Hub events | Async goroutine, 3 attempts/3s backoff. NEW event types MUST be added to hub `allowedEventTypes` or POST /event 400s. **SEVERITY IS AN EXACT WIRE CONTRACT: `{"info","warning","error","critical"}` and nothing else.** The hub silently COERCES any other string to `"info"` (`hub/internal/api/handler.go`, the ingest severity switch) and `severityNotifies` (`hub/internal/notify/dispatcher.go`) emails only warning/error/critical — so a typo'd severity is stored and delivered to NOBODY, with no error anywhere. **`"warn"` is not a severity.** It shipped on `disk_health_degraded` (fixed v0.215.0, R-328) and is STILL live on `app_start_failed` (R-329) |
+| `notify.DiskAlert` / `DiskAlertKind` / `DiskAlertKind.Severity()` | controller/internal/notify/notifier.go | `NotifyDiskHealthDegraded(DiskAlert)` | The disk-health alert payload + its five Hungarian message shapes | The notifier owns customer copy — pass a `DiskAlert`, never a pre-formatted string, or Hungarian scatters across packages. `Severity()` is the ONE mapping kind→hub severity and is exported so any package can assert the contract instead of duplicating the literal |
 | `Notifier.Notify*` convenience methods | controller/internal/notify/notifier.go | typed wrappers (backup/DB/storage/channel/DR…) | Standard events | Add a typed wrapper rather than raw PushEvent calls |
 | `report.BuildReport` / `Pusher.Push` | controller/internal/report/builder.go + pusher.go | periodic hub report | Box→hub reporting | ACK carries `config_version` → `ConfigRefresher.Reconcile` |
 | `report.Trigger` (`NewTrigger`/`Fire`/`Run`) | controller/internal/report/trigger.go | `Fire()` after a hub-relevant user action | THE out-of-cycle report push (v0.139.0) — fire via `api.Router.reportPushNow` / `web.Server.reportTriggerNow`, both nil-safe | Coalesce-and-eventually-fire (trailing edge; quiet 2s, min spacing 15s). NEVER add retries (Pusher owns them); NEVER reuse the `internal/sync` REFUSE-debounce for hub pushes (a refused fire loses the update until the next cycle). Fire only AFTER a successful local commit |