Drop the LibrariesAndTests.slnf split for a one-pass managed build

[jschick04]

What

Replaces the LibrariesAndTests.slnf build split (and the -m:1 workaround) with a single one-pass dotnet build EventLogExpert.slnx. Stacked on #609.

Why

#609 introduced the slnf split so CI could build the libraries+tests separately from the MAUI app, working around a parallel-build race: the RID-qualified app compiles the shared libraries as win-x64 while the tests compile them AnyCPU, so each library is built twice concurrently and races on its obj/bin (CS2012 / MSB3030). The slnf is a maintenance burden (it must list every project). This PR removes the race at the source so the whole solution builds in one parallel pass - no slnf to maintain, matching common .NET practice (PowerToys / eShop / CommunityToolkit build the whole solution/filter in parallel; none use -m:1).

This supersedes #609's "build the app separately" approach. Net effect once both land: one-pass build, no slnf, no -m:1.

How

1. Directory.Build.targets (new) - strips RuntimeIdentifier;SelfContained from every executable's ProjectReference items (GlobalPropertiesToRemove), so the shared libraries build AnyCPU exactly once regardless of the app's RID. The libraries get no RID (the SDK-recommended pattern - pinning a RID on libraries is an anti-pattern); the app keeps its own RID for its per-arch publish -r win-x64/win-arm64 output.
2. Directory.Build.props - global DebugType=embedded, so there is no separate .pdb for dependent projects to race on copying (the second parallel race). dotnet/eShop and CommunityToolkit/Windows use the same setting for the same reason; consistent with this repo's existing helper executable.
3. PullRequest.yml - one dotnet build EventLogExpert.slnx -p:WindowsPackageType=None (managed-only, matching the prior PR-CI coverage; the native shell extension + MSIX remain a release-pipeline concern). Drops the slnf step, the separate "Build app" step, and the now-contradictory "Don't recombine" comment.
4. Deletes LibrariesAndTests.slnf (its only consumer was the rewritten workflow step).

Validation

• Whole-solution parallel build (-p:WindowsPackageType=None): 0 warnings / 0 errors.
• Every shared library (incl. the Razor EventLogExpert.UI) builds AnyCPU (no win-x64 lib output); the app builds win-x64. 0 separate .pdb files.
• Unit tests pass against the one-pass build (--no-build): Logging, DatabaseTools, Runtime (1629), UI (958).
• ElevationHelper self-contained publish (the MSIX path) still produces a working bundle with e_sqlite3.dll + the AnyCPU libraries.
• An earlier validation spike (RID-pin variant) passed CI end-to-end on base Build the app separately from libraries and tests to drop the -m:1 build workaround #609, including the container integration tests.

Out of scope

The separate EventLogExpert-ADO release-pipeline repo still passes -m:1 (its build.yml + two package.yml publish tasks) - a follow-up in that repo. The MSIX-only ElevationHelper publish inside the app csproj retains its own -m:1 (single self-contained publish, not the build-graph one).

[Copilot]

Pull request overview

This PR removes the LibrariesAndTests.slnf split introduced in #609 and restores a single, parallel, whole-solution CI build by preventing RID/self-contained properties from flowing from executable projects into referenced libraries (eliminating the AnyCPU vs win-x64 dual-build race) and by embedding PDBs to avoid parallel copy races.

Changes:

• Add Directory.Build.targets to strip RuntimeIdentifier/SelfContained from ProjectReference builds originating from executable projects.
• Set DebugType=embedded globally in Directory.Build.props to avoid .pdb copy contention under parallel builds.
• Simplify PR CI to a single dotnet build EventLogExpert.slnx ... -p:WindowsPackageType=None step and delete LibrariesAndTests.slnf.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
LibrariesAndTests.slnf	Removes the solution filter now that CI no longer depends on a split build.
Directory.Build.targets	Prevents RID/self-contained properties from propagating to referenced projects when building executables, addressing the root parallel-build race.
Directory.Build.props	Embeds debug symbols across the repo to avoid parallel .pdb copy races.
.github/workflows/PullRequest.yml	Switches PR validation to one-pass whole-solution build and removes the separate app build step.

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