Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@docs/tasks/active/20260411-docx-table-merge-gaps-todo.md`:
- Around line 1-100: Add the missing paired lessons file for this task: create
docs/tasks/active/20260411-docx-table-merge-gaps-lessons.md alongside the
existing 20260411-docx-table-merge-gaps-todo.md; the lessons file should
summarize what was changed (items 1–5), decisions made (readGridSkip,
vMergeTracker.colSpan, orphan-continue promotion, gridSpan clamping, final row
normalization), test coverage added, and any follow-ups (items 6–12) so the task
pair follows the docs/tasks/active/*-{todo,lessons}.md convention.

In `@packages/docs/src/import/docx-importer.ts`:
- Around line 299-300: makeCoveredCell currently creates synthetic cells with
colSpan: 0 which the exporter (docx-exporter.ts) treats as real vertical-merge
continuations and emits <w:vMerge/>, causing bogus merge markup on round-trip.
Update makeCoveredCell in docx-importer.ts to mark these synthetic padding cells
with a distinct flag (e.g., syntheticCover: true) and set colSpan consistently
for real cells; then modify the exporter logic that serializes colSpan === 0 (in
docx-exporter.ts) to only emit <w:vMerge/> when the cell is not marked synthetic
(i.e., check !cell.syntheticCover before serializing vMerge). Apply the same
synthetic flag change to the other synthetic-creation site mentioned (the block
at 412-422) so exporter can distinguish true vMerge continuations from
gridBefore/gridAfter padding.
- Around line 294-300: The code is inserting gridBefore/gridAfter covered cells
even when the table has no tblGrid (numCols === 0); change the logic in
DocxImporter where gridBefore/gridAfter are applied (the blocks that call
DocxImporter.readGridSkip and then push makeCoveredCell based on
gridBefore/gridAfter) to only apply that padding when the table actually has a
grid (e.g., numCols > 0 or an explicit tblGrid present). Update both occurrences
of this pattern (the trPr/readGridSkip → gridBefore/gridAfter → loop that pushes
makeCoveredCell and the similar block later) so that when numCols === 0 you skip
adding these synthetic covered cells and preserve row shape for gridless tables.

In `@packages/docs/test/import/docx-importer.test.ts`:
- Around line 372-426: Add mirror tests for the gridless-table cases by
duplicating the existing w:gridBefore and w:gridAfter test scenarios but remove
the <w:tblGrid> section in each fixture so the importer exercises the "no
tblGrid" path; use the same helpers (createMinimalDocx and DocxImporter.import)
and assert that no synthetic covered cells are inserted (i.e., cells.length
equals the number of provided <w:tc> and any placeholder cells should not be
created — check colSpan === 0 expectations are applied to the correct indices or
omitted as appropriate), and place these new tests alongside the existing
"should pad leading placeholders for w:gridBefore" and "should pad trailing
placeholders for w:gridAfter" tests in the same file to catch the regression.