R-553: four decisions stop reading their own Hungarian words (sites 1-4)

Every Hungarian sentence is byte-identical; each decision now reads a signal set where the message is
made. util.KindErrorf builds the same bytes fmt.Errorf did while carrying a sentinel for errors.Is.

- Deploy status (api/router.go): deployStatusFor() by kind — stacks.ErrAlreadyDeployed (409),
  ErrRequiredField / ErrPathMissing / ErrNotEnoughMemory (400). The „kötelező" / „memória" /
  "does not exist" / "already deployed" text chain is gone.
- Off-site failure class (backup/offbox.go): ErrOffsiteQuota replaces the „tárhelykeretet" match. The
  restic/ssh signatures stay text matches on purpose — that output is not ours and is not translated.
- Alert placement (web/alerts.go): monitor.HealthReport carries WarningKinds parallel to Warnings;
  the "not on a separate drive" warning is inline by KIND. The hub report is untouched (builder.go
  copies Status/Issues/Warnings only) — pinned by a wire test.
- Stale off-site note (web/handlers.go): settings LastWarningKind + backup.OffboxWarnNoAppsSelected.
  The text test survives ONLY for kind == "" (a box whose last run predates 0.251.0) and is removed
  when R-570 closes; slice 2 must not translate that producer before then.

Tests (all red-proofed by restoring the pre-fix predicate — see the audit's redproofs.txt):
TestR553_Deploy_DecisionSurvivesWordingChange, TestR553_DeployHandlerUsesTheKind,
TestR553_DeployProducersCarryKindAndKeepTheirWords (through the real DeployStack),
TestR553_OffsiteQuota_{Decision,HeadLine}SurvivesWordingChange, TestR553_OffboxRunRecordsTheKind,
TestR553_StorageWarningsCarryKindsAndKeepTheirWords, TestR553_DiskWarningPlacementSurvivesWordingChange,
TestR553_HubReportWarningsAreUnchangedOnTheWire, TestR553_StaleNote*, TestR553_WarningKindIsPersistedAndCopied.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0159rPz1ZhFKsS53msqPYxtS

REUSE.md

@@ -37,6 +37,16 @@
 | `parseWWWAuthenticate` + `fetchAnonymousToken` | controller/internal/selfupdate/updater.go | Bearer-challenge parse + anonymous Docker v2 token | Any credential-free registry API access | realm comes FROM THE HEADER (never hardcode a token URL); denial = errAnonymousDenied, never "credentials missing" |
 | `Syncer.runGit` / `runGitInDir` | controller/internal/sync/sync.go | `(args...) error` | git CLI ops | Credentials masked in logs via `maskRepoURL` |
 
+### Error kinds — never branch on a customer-facing sentence (R-553)
+
+| Symbol | File | Short signature | Use for | Gotchas |
+|---|---|---|---|---|
+| `util.KindErrorf` / `util.KindError` | controller/internal/util/errkind.go | `(kind error, format string, a ...interface{}) error` | ANY refusal a caller must tell apart: build the message exactly as `fmt.Errorf` would AND carry a sentinel for `errors.Is` | The message bytes are unchanged (pinned by tests); never `fmt.Errorf("%w: …")`, which would prepend the sentinel's own text to the customer's sentence |
+| `stacks.ErrAlreadyDeployed` / `ErrRequiredField` / `ErrPathMissing` / `ErrNotEnoughMemory` | controller/internal/stacks/deploy_errors.go | sentinels | the API's deploy status code (`api.deployStatusFor`) | 409 / 400 / 400 / 400. Do NOT add a text signature beside them |
+| `backup.ErrOffsiteQuota` | controller/internal/backup/offbox.go | sentinel | `ClassifyOffsiteFailure` telling a quota over-run apart | The other arms of that switch stay TEXT matches on purpose — they are restic's and ssh's own English output, which we neither write nor translate |
+| `monitor.WarnKind*` + `HealthReport.addWarning` / `WarningKindAt` | controller/internal/monitor/healthcheck.go | `(text, kind string)` | a health warning whose PLACEMENT the dashboard decides | Internal only: `internal/report/builder.go` copies Status/Issues/Warnings, so kinds never reach the hub (pinned) |
+| `settings.OffboxTarget.LastWarningKind` + `backup.OffboxWarnNoAppsSelected` | controller/internal/settings/settings.go | persisted string | the Távoli mentés page's stale-note substitution | Written and cleared with `LastWarning`; the text fallback in `offboxWarningDisplay` is LEGACY only (kind == "") and is removed when R-570 closes |
+
 ### HTTP/JSON envelopes + flash messages
 
 | Symbol | File | Short signature | Use for | Gotchas |