[AndreyStartsev]

Problem

ExportReport marks a read as "status": "partial" when stream gzip members fail to decode, are rebuilt by structural recovery, or decode without a matching checksum, or when Global/ElemTable decodes no row — yet the CLI process still exits with code 0 unless a reader limit cut a stream (3). Scripts that require hard failures on partial reads had to parse the JSON report themselves.

Closes #54

Changes

• Add RvtExitCodes.PartialRead = 6 (codes 0..4 and downgrade --check's 5 were already assigned) and strict overloads on RvtExitCodes.ForRead, ExportReport.ForRead, and ExportReport.Failed while preserving existing method signatures.
• Add --strict to rvtio (Program.cs, ExportCommand.cs):
  • Exits with code 6 without writing an incomplete export when status == "partial" without an unaccepted limit hit (LimitExceeded 3 still takes precedence on unaccepted limits; --allow-partial and --strict exclude each other with usage exit code 1).
  • Records limits.strict in ExportReport and populates issues[] with stream-level findings (failed-members, recovered-members, unverified-members) alongside no-rows and streams[].
• Document --strict, exit code 6, limits.strict, issues[] codes, and the case $? scripting example in docs/export-report.md, README.md, docs/public-api.md, and CHANGELOG.md.
• Add unit tests in ExportReportTests and end-to-end process tests in CliExitCodeTests on synthetic .rvt files with intact and damaged partition members.

Export comparison

• Exports without --strict and complete exports with --strict produce identical IFC and JSON outputs.

Verification

• dotnet build RvtIO.slnx -c Release — 0 errors, 0 warnings in src/.
• dotnet test tests/RvtIO.Tests/RvtIO.Tests.csproj -c Release --no-build --filter "FullyQualifiedName~ExportReportTests|FullyQualifiedName~ChunkDecompressorTests|FullyQualifiedName~Cli" — all non-fixture tests passed on net8.0 and net10.0 (private-fixture [SkippableFact] tests skipped when RVTIO_TEST_FILES is unset).
• dotnet docfx docfx.json --warningsAsErrors — 0 warnings, 0 errors.