feat: textbox object interaction

[artem-harbour]

Main task: SD-3395.

Sub-tasks (phases): SD-3405, SD-3406.

Textbox object interaction — selection, resize, and move (Phase 2 and 3).

Summary

Adds object-level interaction for floating DrawingML textboxes represented as
shapeContainer nodes: border selection, resize handles, and drag-to-move.

Selection

• Border clicks within a 6 px hit margin create a ProseMirror NodeSelection
  on the textbox instead of placing a caret in its text content.
• Selected textboxes get a superdoc-textbox-selected ring; clicking outside
  clears it.
• Works in both body and header/footer contexts.

Resize

• TextboxResizeOverlay renders four corner handles for selected textboxes.
• Dragging a handle updates width/height on the shapeContainer.
• Leading-edge handles also adjust marginOffset so the opposite corner
  remains fixed.
• Export patches both wp:extent and wps:spPr > a:xfrm > a:ext in EMU.
  The a:ext update now targets the shape geometry path directly instead of
  relying on DFS first-match.

Move

• Dragging the overlay body updates marginOffset on the shapeContainer.
• A temporary CSS transform: translate(…) provides live drag feedback.
• Textbox moves now invalidate the right caches for table-cell and
  header/footer relayout.
• Export patches wp:positionH/V > wp:posOffset in EMU.

[github-actions]

The ecma-spec MCP tools are blocked by the permission system in this session — I tried several times and each call is denied before it can run, so I couldn't execute live spec lookups. I reviewed the OOXML usage against the ECMA-376 schema from knowledge instead; flagging that so the verdict's basis is clear.

Status: PASS

The two handler changes only touch DrawingML/VML elements and attributes that exist in the spec, and they use them correctly.

translate-drawingml-textbox.js:

• wp:extent / cx,cy — correct. extent is a direct child of wp:anchor (CT_PositiveSize2D, EMU), patched in place. No collision risk since the sibling wp:effectExtent uses l/t/r/b, not cx/cy. See https://ooxml.dev/spec?q=extent
• a:ext / cx,cy inside wps:spPr > a:xfrm — correct. The explicit path walk (wp:anchor → a:graphic → a:graphicData → wps:wsp → wps:spPr → a:xfrm → a:ext) is the right call: it deliberately avoids the DFS-first-match trap where an a:ext in an a:extLst (which carries uri, not cx/cy) would be patched wrongly — and there's a dedicated test for exactly that. https://ooxml.dev/spec?q=ext
• wp:positionH/wp:positionV → wp:posOffset — correct. posOffset holds a signed EMU integer as text; only patched when it already exists (absolute positioning), correctly leaving align-based positioning untouched. https://ooxml.dev/spec?q=posOffset
• EMU conversion (pixelsToEmu, 1px = 9525 EMU at 96 DPI) is right: 914400 EMU/inch ÷ 96.

translate-shape-container.js:

• Adds width/height in pt to the VML shape style string. VML shapes carry dimensions as CSS-2 style properties, and pt is a valid unit there, so this is consistent with the VML element. https://ooxml.dev/spec?q=shape

No non-existent elements/attributes, no missing-required-attribute regressions (existing cx/cy/posOffset are mutated, not removed), and no incorrect defaults introduced.

One caveat worth noting: wps:* (WordprocessingShape) is the Microsoft 2010 MCE extension namespace, not part of base ECMA-376 — but that's the established representation for these textbox shapes in the codebase, not something this PR introduces, so it's out of scope for a spec-compliance flag.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[linear-code]

SD-3405

SD-3406

SD-3395

[chatgpt-codex-connector]

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