[ty] Squash false positive logs for failing to find `builtins` as a real module

I recently started noticing this showing up in the logs for every scope
based completion request:

```
2025-12-11 11:25:35.704329935 DEBUG request{id=29 method="textDocument/completion"}:map_stub_definition: Module `builtins` not found while looking in parent dirs
```

And in particular, it was repeated several times. This was confusing to
me because, well, of course `builtins` should resolve.

This particular code path comes from looking for the docstrings
of completion items. This involves a spelunking that ultimately
tries to resolve a "real" module if the stub doesn't have available
docstrings. But I guess there is no "real" `builtins` module, so
`resolve_real_module` fails. Which is fine, but the noisy logs were
annoying since this is an expected case.

So here, we carve out a short circuit for `builtins` and also improve
the log message.

crates/ty_python_semantic/src/module_resolver/resolver.rs

@@ -265,7 +265,14 @@ fn desperately_resolve_module<'db>(
     let _span = tracing::trace_span!("desperately_resolve_module", %name).entered();
 
     let Some(resolved) = desperately_resolve_name(db, importing_file, name, mode) else {
-        tracing::debug!("Module `{name}` not found while looking in parent dirs");
+        let extra = match module_name.mode(db) {
+            ModuleResolveMode::StubsAllowed => "neither stub nor real module file",
+            ModuleResolveMode::StubsNotAllowed => "stubs not allowed",
+            ModuleResolveMode::StubsNotAllowedSomeShadowingAllowed => {
+                "stubs not allowed but some shadowing allowed"
+            }
+        };
+        tracing::debug!("Module `{name}` not found while looking in parent dirs ({extra})");
         return None;
     };
 

crates/ty_python_semantic/src/types/ide_support.rs

@@ -843,6 +843,7 @@ mod resolve_definition {
     use ruff_db::system::SystemPath;
     use ruff_db::vendored::VendoredPathBuf;
     use ruff_python_ast as ast;
+    use ruff_python_stdlib::sys::is_builtin_module;
     use rustc_hash::FxHashSet;
     use tracing::trace;
 
@@ -1160,6 +1161,14 @@ mod resolve_definition {
         // here because there isn't really an importing file. However this `resolve_real_module`
         // can be understood as essentially `import .`, which is also what `file_to_module` is,
         // so this is in fact exactly the file we want to consider the importer.
+        //
+        // ... unless we have a builtin module. i.e., A module embedded
+        // into the interpreter. In which case, all we have are stubs.
+        // `resolve_real_module` will always return `None` for this case, but
+        // it will emit false positive logs. And this saves us some work.
+        if is_builtin_module(db.python_version().minor, stub_module.name(db)) {
+            return None;
+        }
         let real_module =
             resolve_real_module(db, stub_file_for_module_lookup, stub_module.name(db))?;
         trace!("Found real module: {}", real_module.name(db));