Expose corpus-export reingest mode through REST and chunked imports

[JSv4]

import_corpus_export_for_user(..., reingest_and_remap=True) already supports preserving an export's prepared parsing/structural artifacts when explicitly passed False. The direct REST endpoint and chunked completion path omit that argument, so callers cannot select the existing mode.

Implementation

• Add a validated reingest_and_remap boolean to CorpusExportImportSerializer, defaulting to True for backward compatibility.
• Pass the value through CorpusExportImportView to the existing service.
• Accept and validate the same option in corpus-export chunked-upload metadata. Persist the normalized boolean and pass it through final assembly/completion; handle explicit False correctly rather than using truthiness/defaulting that replaces it.
• Keep authorization, archive validation, destination-corpus behavior, and supported export formats unchanged. Reuse the existing importer and annotation/relationship remapping logic.
• Document the default and the fidelity/processing trade-off. Update any frontend import helper that constructs these requests to preserve an explicitly supplied option.

Acceptance criteria

• Direct and chunked requests with omission or True retain the current reingest behavior.
• Explicit False reaches the importer and preserves supported exported parsing artifacts, structural annotations, annotation IDs/remappings, labels, metadata, and relationships without scheduling a reparse.
• Tests cover boolean serialization, malformed values, unauthorized destinations, chunked resume/completion, and a supported export containing cross-document relationships.
• Use the existing REST/chunked and V2/V3 import regression fixtures; do not introduce a separate import format or pipeline.

Code pointers

serializer; REST view; service option; chunked completion; reingest regression tests.