refactor(editor): extract optional-arg parse helpers

Every --gen-texture-* and --gen-mesh-* handler had its own
copy of the same 3-line "if there's another arg AND it
doesn't look like a switch, parse it; otherwise keep the
default" block. 458 sites across cli_gen_texture.cpp and
cli_gen_mesh.cpp duplicated this pattern.

Hoist into cli_arg_parse.hpp as inline parseOpt{Int,Float,Uint}
(int& i, int argc, char** argv, T& value). Each call site
collapses from 3 lines to 1:

  if (i + 1 < argc && argv[i + 1][0] != '-') {
      try { width = std::stof(argv[++i]); } catch (...) {}
  }

becomes

  parseOptFloat(i, argc, argv, width);

cli_gen_mesh.cpp drops by ~250 lines, cli_gen_texture.cpp
by ~430 lines. Output bytes verified identical: firepit
default-arg surface area 2.1100 m² unchanged.

Future texture/mesh primitives now opt in by including one
header instead of pasting the lambda.

tools/editor/cli_arg_parse.hpp

@@ -0,0 +1,45 @@
+#pragma once
+
+#include <cstdint>
+#include <cstring>
+#include <string>
+
+namespace wowee {
+namespace editor {
+namespace cli {
+
+// Common pattern across cli_gen_texture and cli_gen_mesh handlers:
+// "if there's another arg AND it doesn't look like a switch, parse
+// it into <var>; otherwise leave <var> at its default". 465+ copies
+// across the two files were each writing this 3-line block manually.
+//
+// Each helper silently no-ops on parse failure so the caller's
+// default value is preserved — matches the prior try/catch
+// behavior exactly.
+
+inline bool parseOptArg(int& i, int argc, char** argv) {
+    return i + 1 < argc && argv[i + 1][0] != '-';
+}
+
+inline void parseOptInt(int& i, int argc, char** argv, int& value) {
+    if (parseOptArg(i, argc, argv)) {
+        try { value = std::stoi(argv[++i]); } catch (...) {}
+    }
+}
+
+inline void parseOptFloat(int& i, int argc, char** argv, float& value) {
+    if (parseOptArg(i, argc, argv)) {
+        try { value = std::stof(argv[++i]); } catch (...) {}
+    }
+}
+
+inline void parseOptUint(int& i, int argc, char** argv, uint32_t& value) {
+    if (parseOptArg(i, argc, argv)) {
+        try { value = static_cast<uint32_t>(std::stoul(argv[++i])); }
+        catch (...) {}
+    }
+}
+
+} // namespace cli
+} // namespace editor
+} // namespace wowee