Add form field read-only control and signature interception bridge

[mutumbakato]

Note

Demo / proof-of-concept for the customization approach — not production-ready and not meant to merge as-is. Use it (and the guide) as a reference for customizing an SDK fork.

Summary

Exposes two native PDF form capabilities through NutrientView, on both the Legacy (Paper) and New (Fabric + TurboModule) architectures, following the BRIDGING.md recipe:

• setFormFieldReadOnly(fullyQualifiedName, readOnly, persist?) — locks/unlocks a single form field. iOS maps persist: true to PSPDFFormField.isReadOnly (persisted PDF flag) and persist: false to isEditable (session-only). Android updates AnnotationFlags.LOCKEDCONTENTS on the field's widget annotations, preserving existing flags (READONLY is ignored for widgets, and Android's FormField has no read-only setter).
• interceptSignatureFields prop + onSignatureFieldTapped event — consumes taps on signature form fields (iOS didTapOnAnnotation: delegate, Android FormManager.OnFormElementClickedListener) and emits {fullyQualifiedName, pageIndex} to JS instead of presenting the native signature UI.
• dismissSignaturePad() — dismisses the presented native signature UI, resolving false otherwise (idempotent). Recognizes both the signature creation UI and the saved-signature picker: iOS type-checks the presented navigation stack against PSPDFSignatureCreationViewController, legacy PSPDFSignatureViewController, and PSPDFSignatureSelectorViewController; Android scans candidate fragment managers for ElectronicSignatureFragment and SignaturePickerFragment instances.

Also included:

• A Signature Interception Catalog example used as the runtime test harness.
• An implementation guide for customers customizing an SDK fork.

Verification

• npm test (32/32), npm run lint, npm run build-and-generate-types — all pass.
• Catalog Android assembleDebug (compiles legacy + newarch source sets + codegen) and iOS xcodebuild — both succeed.
• Runtime (Maestro-driven, New Architecture) on a Pixel 9 Pro emulator and iPhone 17 Pro simulator:

Test	Android	iOS
Intercept ON: event fires with correct field/page, native UI suppressed	✅	✅
Intercept OFF: default "Add Signature" UI opens unchanged	✅	✅
dismissSignaturePad() with creation UI open → true, UI closed	✅	✅
dismissSignaturePad() with saved-signature picker open → true, closed	✅	—
dismissSignaturePad() with nothing open → false	✅	✅
Lock blocks editor on the target field only; unlock restores	✅	✅

Known caveat surfaced during testing: form interaction (and therefore interception) requires a writable document — Android file:///android_asset/ documents open read-only. Documented in the guide.

Open items

• Save-and-reopen persistence assertions; multi-widget fields; rotation during signature UI; same runtime matrix on Paper builds and physical devices.
• Decide whether persist: false should reject on Android instead of behaving persistently.