Upgrade to ktsu.Semantics 2.8.0 and simplify path access

[matt-edmondson]

Follow-up to #279.

What 2.8.0 brings

ktsu-dev/Semantics#140 fixed SemanticString<T>.CompareTo(object) so it unwraps ISemanticString instead of handing another semantic string to string.CompareTo(object) — the root cause of #273 — and added WeakString to IPath, IFileName, IFileExtension and IDirectoryName.

Nothing here was required

I verified this before writing any of it: ImGuiApp implements none of those interfaces, so the added interface members break nothing, and the existing code builds and passes all 604 tests against 2.8.0 untouched. Everything below is optional cleanup the new surface makes possible.

• DrawContentRow read the display path by testing for two concrete types and falling back to string.Empty — a branch that could never legitimately be reached, since every entry is one of the two:

  AbsoluteDirectoryPath? directory = path as AbsoluteDirectoryPath;
  AbsoluteFilePath? file = path as AbsoluteFilePath;
  string displayPath = directory?.WeakString ?? file?.WeakString ?? string.Empty;

  IAbsolutePath now carries WeakString directly. (The directory cast stays — it still drives the trailing-separator and navigation branches.)
• SortContents and its tests used ToString(), which returns string? and cost a null-forgiving operator at each of four call sites.

What deliberately did not change

SortContents still sorts on the string value rather than the entry itself. The IComparable<IPath> added in 2.8.0 only helps collections typed as IPath exactly — CurrentContents is a Collection<IAbsolutePath>, which implements IComparable<T> of neither itself nor IPath, so .ThenBy(p => p) would still box through the non-generic CompareTo(object). It would no longer throw, but it would be slower and would lose the case-insensitive display order. The <remarks> on the method now records this.

All four Semantics packages move together, since that repo versions in lockstep.

Verification

Restored, built and tested against the real ktsu.Semantics.* 2.8.0 from nuget.org (not a local build): 603 passed, 1 skipped (the Windows-only drive assertion).

🤖 Generated with Claude Code

https://claude.ai/code/session_01WFRwYRHhEmVMGvrH2BbtbW

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Quality Gate failed

Failed conditions
0.0% Coverage on New Code (required ≥ 80%)

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