Release: publish the two sidecar dotnet tool packages to NuGet

[MelbourneDeveloper]

docs/specs/BINARY-DEPLOYMENT.md describes distributing the C# and F# sidecars as dotnet tool packages, and the sidecar resolution order in src/sharplsp/src/sidecar/manager.rs puts a dotnet tool shim on PATH first — ahead of every bundled layout:

1. sharplsp-sidecar-csharp on PATH   <- "the production distribution path"
2. installed layouts (VSIX / archive / dev)
3. dotnet run --project (dev only)

Nothing publishes those packages. ci-build.yml runs a dotnet pack smoke test, so the projects are known to pack; no job pushes them to nuget.org. docs/plans/DISTRIBUTION-PLAN.md had pack-sidecars and the NuGet publish ticked as done; both have been corrected to [ ] NOT BUILT.

This is not blocking anyone today — the VSIX and the new standalone server archive both ship the sidecars and resolve them by layout — but the code comment calling PATH "the production distribution path" is currently false, and the spec should either be built or amended.

Remaining work:

• Decide whether dotnet tool distribution is still the intended path, or whether [BINARY-DEPLOYMENT] should be narrowed to the archive + package managers
• If keeping it: add a pack-sidecars job to release.yml and push both nupkgs with a NuGet API key on the release environment ([DIST-SECRETS])
• Either way, correct the resolution-order comment in manager.rs so it describes what actually ships