Add Cabrillo import and submission preflight

[rwjblue]

Context

PoLo and mainstream contest loggers can generate Cabrillo for submission. Sidecar should help validate the final artifact without becoming a log editor or claiming to reproduce official adjudication.

The first supported profile should be NAQP CW. The parser and validation boundaries should allow later NAQP modes without becoming a general all-contest engine.

Scope

• Parse the required Cabrillo 3.x headers and NAQP CW QSO records.
• Import a Cabrillo file as a read-only comparison/preflight source.
• Compare the Cabrillo contacts with the active normalized log using conservative identity rules.
• Reuse the event/entry profile and findings model from Add category-aware NAQP compliance diagnostics #28.
• Validate at least:
  • contest identifier and event period
  • callsign and operator/category headers
  • assisted/unassisted category consistency
  • claimed score and QSO count
  • eligible modes and bands
  • sent-name and sent-location consistency
  • received exchange completeness
  • duplicates and obvious self-QSOs
• Distinguish errors, warnings, informational differences, and checks that are not verifiable.
• Never rewrite the Cabrillo file or current source log.
• Keep raw private log content out of normal logs and GitHub fixtures.

Acceptance criteria

• A valid NAQP CW Cabrillo 3.x file parses into a documented internal representation.
• Malformed headers and QSO rows produce line-numbered diagnostics without discarding otherwise reviewable content.
• Header/category values are checked against the persisted entry profile.
• The comparison reports missing, extra, and materially different contacts conservatively.
• Claimed totals are compared with Sidecar results and discrepancies are explained.
• Unsupported contests or versions fail clearly rather than being partially misinterpreted.
• The workflow is read-only and preserves the original file byte-for-byte.
• Sanitized fixtures cover valid, malformed, inconsistent-category, and mismatch cases.
• Documentation explains that preflight is advisory and not official log adjudication.

Related work

• Complete NAQP multiplier metadata and excluded-QSO diagnostics #9 provides claimed scoring and QSO reasons.
• Add category-aware NAQP compliance diagnostics #28 provides category-aware compliance findings.
• Add a problem-QSO review panel #30 can display Cabrillo findings in the problem-QSO review panel.