fix(form): remove widget refs from page Annots on removeField

[cozminv]

What?

Fix PDFForm.removeField() so it removes the widget annotation ref from each page's /Annots array, instead of passing an appearance-stream ref to removeAnnot().

Before (src/api/form/PDFForm.ts):

const widgetRef = this.findWidgetAppearanceRef(field, widget);
page.node.removeAnnot(widgetRef);

After:

const widgetRef = this.doc.context.getObjectRef(widget.dict);
if (widgetRef === undefined) {
throw new Error('Could not find PDFRef for widget annotation');
}
page.node.removeAnnot(widgetRef);

Added unit test "removes widget annotation refs from page Annots arrays" in tests/api/form/PDFForm.spec.ts.

Why?

removeField() currently calls page.node.removeAnnot() with the ref returned by findWidgetAppearanceRef() — an /AP/N appearance stream ref. Page /Annots arrays list widget annotation dict refs. PDFPageLeaf.removeAnnot() matches by exact PDFRef, so the widget entry is never removed. context.delete() then removes the widget object, leaving a dangling /Annots reference.

This was reported in #1001. PR #1002 fixed removal of child widget refs from the document context, but did not fix which ref is passed to removeAnnot().

Impact observed in a form-editor workflow (remove all fields, recreate them):

• Page /Annots count roughly doubled (274 → 524 on an 8-page template; 250 broken refs)
• File size grew ~120 KB without logical changes
• Some createTextField() calls failed with FieldAlreadyExistsError while others left ghost annotations

How?

For each widget returned by field.acroField.getWidgets():

1. Resolve the widget dict ref with this.doc.context.getObjectRef(widget.dict) (same approach already used in findWidgetPage()).
2. Call page.node.removeAnnot(widgetRef) with that ref.
3. Leave the rest of removeField() unchanged (AcroForm removal, kid deletion, context.delete(field.ref)).

Alternatives considered:

• Deleting only the appearance ref from context (Partial Appearance Left Behind After Field Removal #1001 workaround) — does not prune /Annots.
• Manually stripping /Annots in application code — works but every consumer must duplicate the fix.
• Relying on PR Find and remove child widgets from the document context #1002 alone — insufficient; wrong ref is still passed to removeAnnot().

findWidgetAppearanceRef() is unchanged and remains used where appearance streams are needed (e.g. updateFieldAppearances, flatten).

Testing?

• Added "removes widget annotation refs from page Annots arrays" in tests/api/form/PDFForm.spec.ts:
  • Create text field via addToPage()
  • Assert widget ref is present in page /Annots before removal
  • Call form.removeField(tf)
  • Assert widget ref is absent from /Annots and no widget annots remain
• All existing PDFForm tests pass: npm test -- tests/api/form/PDFForm.spec.ts (12/12)
• Manual repro (Node, pdf-lib 1.17.1): create field → removeField → widgetRef no longer in page.node.Annots()

New Dependencies?

No

Screenshots

N/A — structural PDF fix; no visual appearance change in viewers when fields are removed correctly.

Suggested Reading?

Yes — PDF 32000 page annotations (/Annots) vs AcroForm field/widget structure; widget annotations use /Subtype /Widget and are listed on the page, separate from /AP appearance streams.

Anything Else?

• Fixes the root cause described in Partial Appearance Left Behind After Field Removal #1001
• Closes #____ (link issue after filing)
• Community fork cantoo-scribe/pdf-lib appears to already use getObjectRef(widget.dict) in removeField(); this PR brings the same correction to Hopding/pdf-lib master
• Branch: fix/removefield-page-annots
• Files changed: src/api/form/PDFForm.ts, tests/api/form/PDFForm.spec.ts

Checklist

• I read CONTRIBUTING.md (https://github.com/Hopding/pdf-lib/blob/master/docs/CONTRIBUTING.md).
• I read MAINTAINERSHIP.md#pull-requests (https://github.com/Hopding/pdf-lib/blob/master/docs/MAINTAINERSHIP.md#pull-requests).
• I added/updated unit tests for my changes.
• I added/updated integration tests for my changes.
• I ran the integration tests (https://github.com/Hopding/pdf-lib/blob/master/docs/CONTRIBUTING.md#running-the-integration-tests).
• I tested my changes in Node, Deno, and the browser.
• I viewed documents produced with my changes in Adobe Acrobat, Foxit Reader, Firefox, and Chrome.
• I added/updated doc comments for any new/modified public APIs.
• My changes work for both new and existing PDF files.
• I ran the linter (https://github.com/Hopding/pdf-lib/blob/master/docs/CONTRIBUTING.md#running-the-linter) on my changes.

[cozminv]

PR for #1784