feat: add data integrity tests and persistence utilities (#96)

[dguido]

Summary

• Add 14 tests for 4 previously untested functions in types.ts: createPathOrganizer, createLocationEntry, getEntryIndexFromArray, isOldEntry
• Create persistenceUtils.ts module with pure parsing/serialization functions for day logs and .weaudit files
• Add 13 tests for persistence utilities covering parsing, serialization, and roundtrip validation
• Refactor codeMarker.ts to use the new persistence utilities, improving testability

Test plan

• All 149 tests pass (npm test)
• Manual verification: Load extension in VS Code, create a finding, save, reload - data persists correctly
• Manual verification: Check day log updates after marking files audited

🤖 Generated with Claude Code

[dguido]

Phase 2: Entry Lifecycle Tests

This PR now includes Phase 2 implementation adding 50 new unit tests for entry lifecycle operations.

New Utility Modules

Module	Functions	Tests
entryUtils.ts	6	6
locationUtils.ts	6	15
auditingUtils.ts	7	29

What was extracted

Entry CRUD (entryUtils.ts):

• removeEntryFromArray() - Remove entry with result tracking
• addToResolvedEntries() - Add to resolved with default details
• restoreEntryFromResolved() - Move from resolved back to tree
• getUniqueAuthors() - Get unique authors from entries
• restoreAllEntries() - Bulk restore all resolved entries
• deleteAllResolvedEntries() - Bulk delete all resolved

Location Management (locationUtils.ts):

• locationMatches() - 4-property comparison (path, startLine, endLine, rootPath)
• findLocationIndex() - Find location in array
• removeLocationFromEntry() - Remove with cascade detection
• filterEntriesByRootPath() - Filter by workspace root
• filterEntriesByAuthor() - Filter by author
• filterEntriesByAuthorAndRootPath() - Combined filter

Auditing (auditingUtils.ts):

• regionsOverlapOrAdjacent() - Region overlap detection
• mergeRegions() - Merge two overlapping regions
• mergePartiallyAuditedRegions() - Merge all regions for a file
• selectionContainedInRegion() - Check if selection is within region
• splitRegionOnDeselect() - Split region when deselecting middle
• adjustSelectionEndLine() - Handle empty line at cursor
• adjustForEmptyLastLine() - Handle empty last line of file

codeMarker.ts updates

Refactored these methods to use the new utilities:

• deleteAndResolveFinding() → removeEntryFromArray(), addToResolvedEntries()
• restoreFinding() → restoreEntryFromResolved()
• deleteResolvedFinding() → removeEntryFromArray()
• deleteAllResolvedFindings() → deleteAllResolvedEntries()
• restoreAllResolvedFindings() → restoreAllEntries()
• deleteLocation() → removeLocationFromEntry()
• getFilteredEntriesForSaving() → filterEntriesByAuthorAndRootPath()
• mergePartialAudits() → mergePartiallyAuditedRegions()
• addPartiallyAuditedFileFromEditor() → selectionContainedInRegion(), splitRegionOnDeselect()

Test results

199 tests passing (149 existing + 50 new)