[patch] Keep ".." segments that climb above the start in RelativeDirectoryPath.Normalize

[matt-edmondson]

Fixes #288

What changed

RelativeDirectoryPath.Normalize() used to resolve the path against a dummy root (/ or C:\) with Path.GetFullPath, then make it relative again. At the root, .. resolves to the root itself, so every .. that climbed above the starting point was dropped. For example, ../sibling became sibling, which names a different directory.

The segments are now resolved lexically:

• . is dropped.
• .. removes the previous segment when there is one that isn't itself ... Otherwise it is kept.
• The result is joined with the platform separator. An empty result becomes ., which is what the old code returned.

Because no dummy root is involved, the result is the same on every OS. The System.Runtime.InteropServices import is gone, since it was only used to pick that root.

Input	Before	After
../sibling	sibling	../sibling
a/../../b	b	../b
../../x/y	x/y	../../x/y
a/./b/../c	a/c	a/c

Tests

• Normalize_WithOnlyDots_ResolvesCorrectly now checks for exactly ../folder. Before, it only checked that the result contained folder.
• A new data-driven test, Normalize_KeepsParentSegmentsThatClimbAboveTheStart, covers the issue's table plus a/./b/../c and a/...
• With the fix reverted, 4 of the new or tightened cases fail. With the fix, all 25 PathUtilityTests pass, and the whole Paths slice passes (186 passed, 2 skipped).
• Semantics.Paths builds cleanly for every target (net8–10, netstandard2.0/2.1), and the local Sonar analyzer build (.sonarlint/sonar-local.props) is clean too.

🤖 Generated with Claude Code

https://claude.ai/code/session_01MZE6sRR8wRTGhthCM8sL2M

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Generated by Claude Code

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

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