x/tools/gopls: SIGBUS reading string data in os.File.readdir

[adonovan]

#!stacks
"sigpanic" && "os.(*File).readdir"

Issue created by stacks.

This stack gdIvug was reported by telemetry:

• crash/crash
• runtime.throw:+9,+0x37
• runtime.sigpanic:+16,+0x16f
• runtime.memmove:+84,+0xec
• runtime.slicebytetostring:+33,+0x83
• os.(*File).readdir:+62,+0x687
• os.(*File).Readdirnames:+4,+0x23
• path/filepath.readDirNames:+5,+0x3b
• path/filepath.walk:+5,+0x4b
• path/filepath.walk:+26,+0x1cf
• path/filepath.walk:+26,+0x1cf
• path/filepath.Walk:+5,+0x6b
• golang.org/x/tools/gopls/internal/filecache.gc:+55,+0x11f
• golang.org/x/tools/gopls/internal/filecache.getCacheDir.func1.gowrap1:+0,+0x2b
• runtime.goexit:+0,+0x3

golang.org/x/tools/gopls@v0.19.1 go1.24.4 darwin/arm64 vscode (1)