fix: resolve golangci-lint errors

- Add _ = prefix for ignored Close/Remove return values
- Fix unused cmd parameter in runMoleculeReady
- Add nolint:misspell for intentional British "cancelled" spelling
- Update comments to use US spelling where not intentional

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/types/types.go

@@ -434,8 +434,8 @@ var FailureCloseKeywords = []string{
 	"rejected",
 	"wontfix",
 	"won't fix",
-	"cancelled",
 	"canceled",
+	"cancelled", //nolint:misspell // British spelling intentionally included
 	"abandoned",
 	"blocked",
 	"error",