Point .clangd CompilationDatabase at the editable build directory

[aaron-ang]

Summary

.clangd points at build/clangd/, but the editable build writes compile_commands.json to build/debug/ (per the build-dir override in pyproject.toml). Result: clangd has no compile DB to read and reports 'file not found' on every project header in any IDE that uses clangd (VS Code, CLion, etc.).

Repointing .clangd at build/debug aligns it with the actual editable build-dir so the IDE picks up the existing compile_commands.json without a manual symlink.

Notes

Earlier revisions of this PR also patched StructVector::GetEntries deref sites in numpy_scan.cpp / python_conversion.cpp and added duckdb/common/vector/*.hpp includes across three files. Those have since landed via #453 (the variegata merge), so this PR is now a single-line .clangd change.

The remaining upstream-side breakage of the editable / Debug build — missing create_*_info.hpp includes that cause dynamic_cast to forward-declared types in D_ASSERT — is tracked separately in duckdb/duckdb#22551. Once that lands and the submodule pin is bumped, the editable build per CLAUDE.md will be green end-to-end.

Test plan

• After this change, opening any project .cpp file in VS Code with the clangd extension resolves all duckdb/... and duckdb_python/... includes against the existing build/debug/compile_commands.json — no symlink needed.

[evertlammerts]

Closing in favor of #453

[aaron-ang]

Hi @evertlammerts, heads-up that on a fresh checkout of main (f1ee06f) the CLAUDE.md two-step editable build still doesn't produce a working debug install. With DISABLE_UNITY=1 (this repo's editable override), the engine fails to compile because many .cpp files call info.Cast<CreateXxxInfo>() without including the matching duckdb/parser/parsed_data/create_xxx_info.hpp, so the D_ASSERT(reinterpret_cast<...> == dynamic_cast<...>) inside ParseInfo::Cast<T>() can't dynamic_cast to a forward-declared type. Submodule pin 01eda16d6e and duckdb/duckdb main both still have this, tracked upstream in duckdb/duckdb#22551. Separately, .clangd still points at build/clangd/, but no documented target populates that directory (editable writes to build/debug/), so clangd can't find a compile DB and reports 'file not found' on every project header in any IDE that uses it.

Happy to reopen or re-scope if a different approach is preferred (e.g. documenting the symlink in CLAUDE.md, or shipping a .vscode/settings.json snippet). Wheel and cibuildwheel builds are unaffected since unity hides both.