fix: Phase 2 — HIGH #6,9,10,11,12,19,23,32,46,47

Files modified (5):
  compiler/gengo/gengo.go — #6,#32: Deduplicate 3 Generate functions into 1
    doGenerate(file, debug, library) replaces 170 lines of copy-paste
    Dead GenerateDebug method removed
  cmd/five/main.go — #9,10,11,12: Fix 5 silently ignored errors
    filepath.Abs, tidy.Run, tidyCmd.CombinedOutput now checked
  hbrtl/strings.go — #19: Str() now reads caller's nWidth/nDec params
    Was ignoring explicit Str(123, 10, 2) arguments
  compiler/pp/pp.go — #46: Fix stale "NOT implemented" comment
    #47: Extract maxIncludeDepth constant
  compiler/lexer/lexer.go — #23: Remove unused LookupKeyword result

Issues resolved: 10 (HIGH: 7, MEDIUM: 3)
Total fixed: 26/53

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

compiler/pp/pp.go

@@ -11,9 +11,8 @@
 //   #ifdef NAME / #ifndef NAME / #else / #endif — conditional compilation
 //   #pragma               — compiler hints
 //
-// #command/#translate (used by hbclass.ch) is NOT implemented yet.
-// Five handles CLASS syntax natively in the parser, so hbclass.ch
-// is not strictly required. But #include is needed for user headers.
+// #command/#translate is supported via command.go (pattern matching + substitution).
+// Five also handles CLASS syntax natively in the parser.
 package pp
 
 import (
@@ -78,9 +77,11 @@ func (pp *Preprocessor) Process(filename, source string) (string, []string) {
 	return result, pp.errors
 }
 
+const maxIncludeDepth = 20
+
 func (pp *Preprocessor) processLines(filename, source string, depth int) string {
-	if depth > 20 {
-		pp.errors = append(pp.errors, fmt.Sprintf("%s: #include depth exceeded (max 20)", filename))
+	if depth > maxIncludeDepth {
+		pp.errors = append(pp.errors, fmt.Sprintf("%s: #include depth exceeded (max %d)", filename, maxIncludeDepth))
 		return source
 	}