[mrcsin]

Problem

The clipboard paste path (ClipboardSerializer.DeserializeSteps) raised free-text Result.Fail(string) / new Error(string) for every parse failure, so a paste error rendered raw English regardless of culture. It reaches the panel via ClipboardViewModel.PasteStepsAsync → ReportFailure, which localizes by type.

What changed

Type the clipboard path, reusing the shared tabular-parse errors 5b introduced (AtRowError, AtColumnError, ActionColumnEmptyError, ActionValueNotIntegerError, ActionByIdNotFoundError, ActionColumnNotFoundError) and adding three clipboard-specific classes:

• ClipboardParseFailedError — Rule-B exception-envelope for the top-level parse catch. Injects ILogger<ClipboardSerializer> and LogWarnings the exception detail (mirrors CsvService), since the localized headline drops ex.Message; the catch is real (CsvHelper throws BadDataException on malformed pastes).
• ColumnCountMismatchError and NoValidStepsError — leaves, byte-identical English.

The value chain composes AtRowError → AtColumnError → PropertyValueParseError: pasting a non-numeric cell into a float column renders, under ru, Строка 1: Столбец «task»: Не удалось разобрать «abc» как float — Russian end to end (was just "Row 1"). This completes the CSV+clipboard ingress: after it, only the config-load-culture boundary is English by design.

Behavior-preserving for English except three flagged changes (same shape as 5b): AtRowError gains : {inner}, the ActionByIdNotFoundError reuse rewords unknown-action, and ClipboardParseFailedError drops : {ex.Message} (kept in the log via logger.LogWarning).

Verification

• dotnet build SemiStep.slnx — 0 warnings.
• dotnet test SemiStep/SemiStep.Tests/SemiStep.Tests.csproj — 1638 passed, 0 failed.
• The composition payoff: CsvDeserializationTests deserializes 20\t5.0\tabc\tc through the real ClipboardSerializer.DeserializeSteps and asserts the full Russian chain under ru. The three new types are each pinned end-to-end: ClipboardParseFailedError (unescaped-quote → BadDataException catch), NoValidStepsError (empty input), ColumnCountMismatchError (too-many-columns). ReasonLocalizerTests pins the 3 ru renders + the en Localize == .Message.
• Review chain: comprehensive (5 agents, all OUTCOME ACHIEVED) → smells → comment audit → critical, all clean after low fixes (end-to-end type pins, a doc logger ref, a comment trim).
• Manual test (operator): pasted TSV with a bad cell / too many columns / malformed quoting under the Russian UI — the error shows in Russian with row/column context.

Per-task commits before collapse

701b397 test: trim redundant tail from clipboard payoff comment
1cb96b3 docs: correct clipboard logger reference in error-reporting
27249bb test(l10n): pin clipboard parse-failed and no-valid-steps error types
44554f1 test(l10n): cover clipboard import error localization end-to-end
b82a87e feat(l10n): type clipboard import errors

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