perf: add fast path checks when resolving config (#437)

- part of #295

For a directory with ~860 files in it, a ~26% improvement:

<img width="1185" height="239" alt="Screenshot 2025-11-18 at 12 18 22 AM" src="https://github.com/user-attachments/assets/01b05dd9-6c83-4669-a4ce-8471afe9ef40" />

I tested a subset of `kibana` locally on my laptop that had 6.6k files in it and it was a much more modest improvement of about 4%. So this is a "small project" optimization that will largely benefit small libraries or projects, and will slightly improve performance for large monorepos.

Here are some examples running on the same set of ~850 files in each case:

### Before

Taking up over a gigabyte in total allocations, and represents over 40% of all allocations:

<img width="713" height="286" alt="Screenshot 2025-11-18 at 12 12 17 AM" src="https://github.com/user-attachments/assets/6b44863c-98a8-4dfd-9292-e9b365aefa8d" />

<img width="1227" height="350" alt="Screenshot 2025-11-17 at 11 27 19 PM" src="https://github.com/user-attachments/assets/cbcd14c5-9ba7-4408-b124-f140cbbc3748" />

### After

Takes up only 0.6% of the total allocations and a few megabytes:

<img width="467" height="211" alt="Screenshot 2025-11-18 at 9 56 06 AM" src="https://github.com/user-attachments/assets/69d88e09-d9bd-4194-a600-845ddd065cbd" />

<img width="546" height="279" alt="Screenshot 2025-11-18 at 9 54 53 AM" src="https://github.com/user-attachments/assets/c15fae1b-82ff-42e2-92b4-5fac1736306e" />

Author: camchenry

internal/utils/find_tsconfig.go

@@ -1,7 +1,9 @@
 package utils
 
 import (
+	"path/filepath"
 	"slices"
+	"strings"
 
 	"github.com/microsoft/typescript-go/shim/core"
 	"github.com/microsoft/typescript-go/shim/project"
@@ -106,8 +108,38 @@ func (r *TsConfigResolver) findConfigWithReferences(
 				}
 			}
 
-			if slices.ContainsFunc(config.FileNames(), func(fn string) bool {
-				return r.toPath(fn) == path
+			if slices.ContainsFunc(config.FileNames(), func(file string) bool {
+				// Fast checks:
+				// 1) check if the strings happen to already be equal (subject to case sensitivity of FS)
+				// 2) check if the base names are equal (subject to case sensitivity of FS)
+
+				// If we're on a case-insensitive FS and the strings are equal, we can return true immediately,
+				// no need to allocate and do any path conversions.
+				if r.fs.UseCaseSensitiveFileNames() {
+					if file == string(path) {
+						return true
+					}
+				} else {
+					if strings.EqualFold(file, string(path)) {
+						return true
+					}
+				}
+
+				// If the base names don't match, we can return false immediately.
+				pathBaseName := filepath.Base(string(path))
+				fileBaseName := filepath.Base(file)
+				if r.fs.UseCaseSensitiveFileNames() {
+					if fileBaseName != pathBaseName {
+						return false
+					}
+				} else {
+					if !strings.EqualFold(fileBaseName, pathBaseName) {
+						return false
+					}
+				}
+
+				// Finally, do a full path conversion and comparison (note: this allocates)
+				return r.toPath(file) == path
 			}) {
 				return true, true
 			}