Canonicalize VectorClock zero-counter entries

[dexcompiler]

Summary

• canonicalize explicit zero-counter VectorClock entries away during parse/read
• keep the internal VectorClockBuilder from reintroducing zero-counter entries during merges
• add C# and F# coverage for zero-as-absence semantics and repeated property stability

Validation

• dotnet test tests/Clockworks.Tests.csproj --filter VectorClockTests -v minimal
• dotnet test property-tests/Clockworks.PropertyTests.fsproj --filter FullyQualifiedName~VectorClockProperties -v minimal
• repeated VectorClock property suite runs
• dotnet test Clockworks.sln -v minimal -m:1
• npm run docs:build
• dotnet pack src/Clockworks.csproj -c Release -v minimal

Fixes #76

[dexcompiler]

@copilot review this pr

[Copilot]

@copilot review this pr

Reviewed at 5cd2b06. I re-ran the VectorClock unit and property test suites and checked the two PR commits; the zero-counter canonicalization and builder-merge behavior look correct, and I didn’t find additional changes needed.

[dexcompiler]

@claude[agent] review this pr

[Claude]

@claude[agent] review this pr

Reviewed at 5cd2b06. The implementation correctly handles zero-counter canonicalization across all entry points:

Implementation (a7f1cc6)

• VectorClock.cs:377-385,399 - ReadFrom tracks hasZeroCounter and skips fast path when present
• VectorClock.cs:464-465,473-474,481-482 - CreateCanonical filters zero counters in single-entry, multi-entry, and empty-result cases
• VectorClockBuilder.cs:130-131 - MergeEntry early-returns on zero counters to prevent reintroduction during merge operations
• Tests validate string/binary parse paths, empty-clock edge case, and structural equality

Documentation (5cd2b06)

• CHANGELOG.md and docs/changelog.md correctly classify this as a bug fix (structural equality now matches vector-clock semantics)
• docs/guide/vector-clock.md updated to document zero-counter canonicalization alongside existing duplicate-deduplication behavior

Validation

• All 45 VectorClock unit tests pass
• All 11 VectorClock property tests pass (including new zero-canonicalization property)
• Full test suite: 232 tests pass
• Documentation builds successfully
• Release package builds successfully

The changes are complete and correct. No additional changes needed.