Failing backend test: copyPadWithoutHistory produces empty/wrong body for nested lists

[JohnMcLear]

Failing test: copyPadWithoutHistory > creates a new pad with the same content as the source pad and copyPadWithoutHistory > source and destination attribute pools are independent
File: src/tests/backend/specs/api/pad.ts:609-707
Status on develop HEAD (b96e262): failing — reproducible locally.

What the test does

Creates a source pad with ulHtml (nested ordered + unordered lists), calls copyPadWithoutHistory to clone it, then fetches the destination via getHTML and asserts the HTML round-trips.

What happens

Same <ol> start-attribute drift as #7786 (cross-reference): the destination pad's exported HTML drops start="2" from the inner nested <ol>:

+ actual:    <ol start="1" class="number"><li>item<ol class="number"><li>item1
- expected:  <ol start="1" class="number"><li>item<ol start="2" class="number"><li>item1

The earlier returns a successful response test (the same describe block) succeeds, so copyPadWithoutHistory does write something — but the resulting content doesn't round-trip cleanly through getHTML.

Likely shared root cause

Probably the same export-side bug as #7786. The copyPadWithoutHistory path serialises the source's atext into an HTML changeset via the import pipeline, then exports it back via the same nested-<ol> walker. Fixing #7786 (export-side start attribute propagation) probably fixes this too — worth verifying with the same fix.

Reproduction

NODE_ENV=production npx mocha --import=tsx --require ./tests/backend/diagnostics.ts \
    --timeout 60000 tests/backend/specs/api/pad.ts

Look under copyPadWithoutHistory.