Playwright e2e tests for multi-column form layout

[harshtandiya]

Context

Multi-column layout (row/column/cell axes) shipped in feat/columns_support. Manual QA covered the cases in plan.md §Chunk 8 but no automated coverage exists. e2e infra is set up (frontend/playwright.config.ts, helpers in frontend/e2e/helpers/) — extend it.

Scope

New file: frontend/e2e/specs/form-layout.spec.ts.

Helper extensions in frontend/e2e/helpers/form-builder.ts:

• fieldCard(label), ejectField(label)
• dragFieldToColumnZone(sourceLabel, atRow, atCol)
• dragFieldToRowZone(sourceLabel, atRow)
• dragFieldOntoCell(sourceLabel, targetLabel, position)
• rowCount(), columnCount(rowIdx), cellCount(rowIdx, colIdx)

Test cases

#	Description
1	Drop field onto existing field cell stacks it into that column
2	Drop on ColumnDropZone creates a new column
3	Drop on RowDropZone creates a new row
4	Eject button on multi-cell column moves cell to new row
5	Cross-row drag collapses source column when emptied
6	Within-column reorder renumbers cell_index
7	Mobile viewport stacks columns vertically (/p/<route>)
8	Conditional-visibility hides field + collapses empty column

Drag mechanics

SortableJS + Playwright: synthetic locator.dragTo() often misses swap thresholds. Use real mouse path:

await page.mouse.move(srcX, srcY);
await page.mouse.down();
await page.mouse.move(midX, midY, { steps: 8 });
await page.mouse.move(dstX, dstY, { steps: 8 });
await page.mouse.up();

May need forceFallback: true on <draggableComponent> in FormBuilderContent.vue for deterministic headless behavior. Test early, tag flaky cases test.fixme until stable.

[harshtandiya]

Superseded by #119. All 8 test cases from the scope shipped in frontend/e2e/specs/form-layout.spec.ts (names match 1:1):

• cell stacks into existing column on drag
• column drop zone creates new column
• row drop zone creates new row
• eject moves cell to new row
• cross-row drag collapses source column
• within-column reorder renumbers cell_index
• mobile viewport stacks columns vertically
• hidden field unmounts, no empty column

Closing.