fix(extract): keep committed palette skeletons out of stale cleanup (#96)

Extract skips writing *palcus.itp back to source (build projects them from blueprints, #50), but the skip branch never marked the skeleton target as desired, so cleanupStaleFiles deleted the committed source/palettes/*.itp.json on every extract — shipping modules with empty custom palettes. Fix marks the skipped target desired; regression test builds a module with a committed skeleton and asserts extract leaves it in place.

🤖 Generated with [Claude Code](https://claude.com/claude-code)Reviewed-on: #96

Co-authored-by: vickydotbat <vickydotbat@tutamail.com>

internal/pipeline/extract.go

@@ -126,8 +126,14 @@ func extractArchiveResources(p *project.Project, archive erf.Archive, desired ma
 		}
 		// *palcus.itp are Toolset-generated palette projections; the module
 		// build regenerates them from source blueprints, so extraction never
-		// writes them back into source.
+		// writes them back into source. The committed skeleton still has to
+		// survive stale cleanup, so mark its target as desired.
 		if ext == "itp" && isPaletteProjectionResref(resource.Name) {
+			effective := p.EffectiveConfig()
+			target, err := extractionTarget(p, "paths.source", effective.Paths.Source, p.SourceDir(), sourceSubdir(ext), strings.ToLower(resource.Name)+"."+ext+".json")
+			if err == nil {
+				desired[target] = struct{}{}
+			}
 			skippedCount++
 			continue
 		}