chore: remove stale repo files and refresh slnx

[philippemnoel]

Summary

Janitorial cleanup of files left behind by earlier renames (PRs #29 and #30) and the workflow refactor (#34).

Delete

• EFCore.ParadeDB.PgSearch.sln.DotSettings, EFCore.PgSearch.sln.DotSettings, ParadeDB.EntityFrameworkCore.sln.DotSettings — Rider/ReSharper per-solution settings files tied to solution names that no longer exist (the live solution is ParadeDB.EFCore.slnx).
• dotnet-tools.json (root) — empty {"tools": {}} stub. The active manifest is .config/dotnet-tools.json, which is the canonical location dotnet tool restore reads from (and what the new lint job in CI uses to load csharpier).

Rename

• ParadeDB.EFCore.sln.DotSettings → ParadeDB.EFCore.slnx.DotSettings so Rider matches it to the current .slnx solution file. (Contents: a small spelling dictionary with paradedb, jieba, Stopwords.)
• Note: git's rename-detection picked a different source-of-rename in the diff because all four *.DotSettings files had near-identical content. The end state is correct — one settings file at the new name, three deletions.

Update ParadeDB.EFCore.slnx

• Drop the now-deleted root dotnet-tools.json reference; add .config/dotnet-tools.json instead.
• Replace publish.yml (deleted in chore: add standard ParadeDB ORM repository scaffolding #34) with release.yml.
• Add the new lint workflows and the root scaffolding files (CHANGELOG, CLAUDE, CONTRIBUTING, NUGET-README, RELEASE) to the IDE Solution folder so they surface in Rider/VS.

Source-code sweep

A full sweep of src/ParadeDB.EFCore/ for unused public APIs / dead code turned up nothing. Every public type, factory method, enum member, translator, and internal type-mapping is referenced from tests, examples, or the DI-registered query pipeline. The library source is left untouched.

Not touching

• assets/paradedb-logo.png — still packed into the NuGet package as <PackageIcon> via src/Directory.Build.props:13. Keeps it.
• .config/dotnet-tools.json — active (csharpier).
• .editorconfig, .csharpierignore — active.

Test plan

• CI passes (especially the Lint job, which depends on .config/dotnet-tools.json).
• Open the repo in Rider/VS: ParadeDB.EFCore.slnx loads, Solution folder shows the refreshed file list, no broken references.
• dotnet tool restore and dotnet csharpier check . still work locally with the root dotnet-tools.json gone.