feat(form-fill): FormFill tool with context and UI components for PDF form filling (#5711)

frontend/src/core/tools/formFill/FormFieldOverlay.tsx

@@ -0,0 +1,20 @@
+/**
+ * FormFieldOverlay stub for the core build.
+ * This file is overridden in src/proprietary/tools/formFill/FormFieldOverlay.tsx
+ * when building the proprietary variant.
+ */
+
+interface FormFieldOverlayProps {
+  documentId: string;
+  pageIndex: number;
+  pageWidth: number;
+  pageHeight: number;
+  fileId?: string | null;
+}
+
+export function FormFieldOverlay(_props: FormFieldOverlayProps) {
+  // Core build stub — renders nothing
+  return null;
+}
+
+export default FormFieldOverlay;

frontend/src/core/tools/formFill/FormFieldSidebar.tsx

@@ -0,0 +1,17 @@
+/**
+ * FormFieldSidebar stub for the core build.
+ * This file is overridden in src/proprietary/tools/formFill/FormFieldSidebar.tsx
+ * when building the proprietary variant.
+ */
+
+interface FormFieldSidebarProps {
+  visible: boolean;
+  onToggle: () => void;
+}
+
+export function FormFieldSidebar(_props: FormFieldSidebarProps) {
+  // Core build stub — renders nothing
+  return null;
+}
+
+export default FormFieldSidebar;

frontend/src/core/tools/formFill/FormFillContext.tsx

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+/**
+ * FormFillProvider stub for the core build.
+ * This file is overridden in src/proprietary/tools/formFill/FormFillContext.tsx
+ * when building the proprietary variant.
+ */
+import React, { createContext, useContext } from 'react';
+
+interface FormFillContextValue {
+  state: {
+    fields: any[];
+    values: Record<string, string>;
+    loading: boolean;
+    error: string | null;
+    activeFieldName: string | null;
+    isDirty: boolean;
+    validationErrors: Record<string, string>;
+  };
+  fetchFields: (file: File | Blob, fileId?: string) => Promise<void>;
+  setValue: (fieldName: string, value: string) => void;
+  setActiveField: (fieldName: string | null) => void;
+  submitForm: (file: File | Blob, flatten?: boolean) => Promise<Blob>;
+  getField: (fieldName: string) => any | undefined;
+  getFieldsForPage: (pageIndex: number) => any[];
+  getValue: (fieldName: string) => string;
+  validateForm: () => boolean;
+  reset: () => void;
+  fieldsByPage: Map<number, any[]>;
+  activeProviderName: string;
+  setProviderMode: (mode: 'pdflib' | 'pdfbox') => void;
+  forFileId: string | null;
+}
+
+const noopAsync = async () => {};
+const noop = () => {};
+
+const FormFillContext = createContext<FormFillContextValue | null>(null);
+
+export const useFormFill = (): FormFillContextValue => {
+  const ctx = useContext(FormFillContext);
+  if (!ctx) {
+    // Return a default no-op value for core builds
+    return {
+      state: {
+        fields: [],
+        values: {},
+        loading: false,
+        error: null,
+        activeFieldName: null,
+        isDirty: false,
+        validationErrors: {},
+      },
+      fetchFields: noopAsync,
+      setValue: noop,
+      setActiveField: noop,
+      submitForm: async () => new Blob(),
+      getField: () => undefined,
+      getFieldsForPage: () => [],
+      getValue: () => '',
+      validateForm: () => true,
+      reset: noop,
+      fieldsByPage: new Map(),
+      activeProviderName: 'none',
+      setProviderMode: noop,
+      forFileId: null,
+    };
+  }
+  return ctx;
+};
+
+/** No-op stub for core builds */
+export function useFieldValue(_fieldName: string): string {
+  return '';
+}
+
+/** No-op stub for core builds */
+export function useAllFormValues(): Record<string, string> {
+  return {};
+}
+
+export function FormFillProvider({ children }: { children: React.ReactNode }) {
+  // In core build, just render children without provider
+  return <>{children}</>;
+}
+
+export default FormFillContext;

frontend/src/core/tools/formFill/FormSaveBar.tsx

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+/**
+ * FormSaveBar stub for the core build.
+ * This file is overridden in src/proprietary/tools/formFill/FormSaveBar.tsx
+ * when building the proprietary variant.
+ */
+
+interface FormSaveBarProps {
+  file: File | Blob | null;
+  isFormFillToolActive: boolean;
+  onApply?: (filledBlob: Blob) => Promise<void>;
+}
+
+export function FormSaveBar(_props: FormSaveBarProps) {
+  return null;
+}
+
+export default FormSaveBar;