Fix list numbering counters and per level indentation

[mantissaman]

Closes #12 and closes #13. Both were found rendering the file attached to #3, and both are verified by rendering it again.

Numbering counters, #12

Counters were keyed on num_id. That is the numbering instance, not the list.

Pandoc and LibreOffice emit a separate w:num per list block and point them all at a single w:abstractNum. The file in #3 is exactly that:

numId 4 -> abstract 1     <- "List item 1"
numId 1 -> abstract 1     <- "List item 2"

Two instances, one list. Keying on the instance gave each its own counter, so both items rendered as 1..

Counters are now keyed on the abstract definition. Lists that really do have separate abstract definitions still restart independently, and there is a test for each direction so the fix cannot drift into the opposite bug.

Level indentation, #13

A w:lvl carries its own w:pPr, and that is where the per level indent lives. We parsed it into CT_Lvl::ppr and then never looked at it, so every level of a list drew at the same left position. In the #3 file the levels ask for 720 and 1440 twips and both rendered at the same place.

Level properties are now merged between the paragraph style and direct formatting, which is where they belong in the property chain. A level indent applies unless the paragraph sets its own.

Result

Rendering office2pdf_test.docx from #3.

Before:

1.    List item 1
1.    List item 2
o     List item
o     List item

After:

    1.    List item 1
    2.    List item 2
            o    List item
            o    List item

That matches the LibreOffice reference in #3.

Checks

cargo fmt --all --check, cargo clippy --workspace --all-targets -- -D warnings and the full suite all pass. 336 tests, up from 333, with three added here.

Scope

Deliberately does not touch #10 or #11, the other two halves of #3. #10 is in the same function PR #2 is rewriting and should wait for that to land.

[mantissaman]

Rebased onto current main and added the baseline update, because the Output stability job had not run on this PR when it was opened. It landed on main with the sprint merge afterwards.

It does fail on the original commit, as expected. Applying a numbering level's own indent moves list markers, so letter:page1.png and contract:page1.png both change.

I checked the delta rather than just regenerating. Rendering both samples before and after, the only visual difference is list markers moving to their level indent, with wrapped text now aligning under the text start instead of returning to the margin. Nothing else on either page moved.

One detail worth recording: the docx part hashes are untouched, numbering.xml included. So this is purely a rendering change and does not alter the OOXML we write, which is what you would want from a fix in the layout engine.

Baseline updated with an audit reason. All seven checks now pass.