Final sweep: Crucible fixes, Path Tracer polish, forge progress, tests green.

Align dashboard subtitle default and UpsertAgent tests with fleet label behavior; WebSocket coalesce and PathForge hardening; Crucible expanded ops and visual DV fixes; Vitest 610/610 and full test-suite pass; trim PROBLEMS.md to open items only.

server/internal/builder/pathforge.go

@@ -125,7 +125,11 @@ func (h *PathForgeHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 
 	res := &PathForgeResult{}
 
+	ctx := r.Context()
 	err = filepath.WalkDir(req.RootPath, func(path string, d os.DirEntry, err error) error {
+		if ctx.Err() != nil {
+			return ctx.Err()
+		}
 		if err != nil || d.IsDir() {
 			return nil
 		}