feat(msldbbuilder): add FASTA->.msl spectral-library builder for ManySearch

Offline library compiler for MetaMorpheus's ManySearchTask: digests protein
FASTAs once and writes compact indexed .msl libraries (precursor mass + charge +
Chronologer iRT + sequence, lean / fragment-less by default) so the parallel
search reads pre-built libraries instead of re-digesting thousands of FASTAs at
search time. Supports per-database output, a merged db|accession-tagged index,
and size-balanced sharded production builds with a global persisted iRT cache.

Added as a new project under mzLib/MslDbBuilder referencing UsefulProteomics-
Databases and Readers. Depends on the .msl writer/reader API from #1036, so its
base is mzlib_speclib.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: trishorts

mzLib/MslDbBuilder/MslDbBuilder.csproj

@@ -0,0 +1,25 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+    <Nullable>disable</Nullable>
+    <ImplicitUsings>disable</ImplicitUsings>
+    <Platforms>x64</Platforms>
+    <PlatformTarget>x64</PlatformTarget>
+  </PropertyGroup>
+
+  <!-- The .msl writer + digestion live in these mzLib projects. -->
+  <ItemGroup>
+    <ProjectReference Include="..\UsefulProteomicsDatabases\UsefulProteomicsDatabases.csproj" />
+    <ProjectReference Include="..\Readers\Readers.csproj" />
+  </ItemGroup>
+
+  <!-- Direct ref so the libtorch native libs (torch_cpu/c10/...) deploy to THIS project's output.
+       The TorchSharp native-deployment target fires for the direct referent, not transitively. -->
+  <ItemGroup>
+    <PackageReference Include="libtorch-cpu" Version="2.5.1" />
+    <PackageReference Include="TorchSharp" Version="0.105.1" />
+  </ItemGroup>
+
+</Project>