F# sidecar loads only the first .fsproj discovered — multi-project F# workspaces mostly unanalyzed

From the multi-agent audit (sidecars/SharpLsp.Sidecar.FSharp/FSharpWorkspace.fs ~167): workspace load picks the FIRST .fsproj found, in filesystem-enumeration order. A solution with several F# projects gets exactly one loaded — files from the others check against a synthetic single-file project (no project references, wrong defines), so cross-project navigation and diagnostics silently degrade, and WHICH project wins is nondeterministic across machines.

F# is a first-class citizen: this needs parity with the C# sidecar's whole-solution load — enumerate every .fsproj in the .sln/.slnx (the shared solution reader already exists), maintain FSharpProjectOptions per project, and route file requests to their owning project.

The new e2e fixture create_medium_workspace() (tests/e2e_modules/fixtures_medium.rs) provides a mixed solution to extend for this.

Start with sidecars/SharpLsp.Sidecar.FSharp/FSharpWorkspace.fs around the workspace-loading logic, then compare it with the C# sidecar's whole-solution behavior and the shared solution reader. Extend tests/e2e_modules/fixtures_medium.rs via create_medium_workspace() to cover multiple F# projects. Done means every project is loaded with its own options and file requests route to the owning project.