Preserve results across syntax provider failures

[stef-k]

Summary

• preserve independent LOC, Markdown, and unaffected syntax results when one selected source file has known syntax/provider unavailability
• emit an explicit incomplete result with structured paths, guard completeness, stable scope accounting, and blocking exit 3
• preserve strict direct analysis and propagate unexpected programming errors

Closes #115

Contract

Incomplete runs use overall: incomplete, retain the completed aggregate separately, preserve authoritative findings, and mark only affected syntax guards incomplete. Successful output keeps its existing schema and bytes. --ci never makes unavailable evidence successful.

The syntax pipeline continues only for SyntaxAnalysisError and ProviderUnavailableError. Arbitrary exceptions, including unexpected concrete-parser exceptions, retain the existing abort boundary.

Validation

• focused provider isolation — 6 passed
• strict production analysis — 26 passed
• completed-output compatibility suites — passed
• python -m unittest discover -s tests — 312 passed
• freshly built disposable wheel installed successfully
• installed-package syntax smoke — passed
• disposable-wheel code-guard . --ci — exit 0 with visible non-blocking REVIEW
• LOC baseline absent and not a symlink
• python -m compileall -q src skills research tests — exit 0
• git diff --check origin/main...HEAD — exit 0

Review

Independent review found and blocked overly broad concrete-parser exception wrapping. The remediation narrows translation to RuntimeError, proves arbitrary exception identity propagation through the real provider boundary, and passed independent re-review at 4e7ea2cf176b30b06713e319ce918b1f78e74f58.