Pre-release fixes and 0.3.0 (#86, #83 follow-ups)

[dvejsada]

Closes #86.

These are the last fixes before 0.3.0, plus the version bump. Each change was implemented in its own worktree by a subagent, then reviewed, re-verified and merged here. A final review then led to one more fix.

1. A nested item's unclosed fence keeps its blank lines (#86)

Cause: in parser._scan_list, take a continuation line of an item nested on its parent's first line (- 1. z then a). It set paragraph, the flag for the current item's own open paragraph. A following sibling, ` 2. ```, then counted as a marker that may not interrupt that paragraph, so it was read as text. The outer scan never saw the item or its fence, and the blank line after the unclosed fence fell out of the enclosing item.

Fix: nine lines. Such a continuation line no longer claims the paragraph as the item's own. * 2. z\na\n 1. ```\n\n now round-trips.

Tests: 10 parametrized shapes, a round-trip test and an interruption-control test. They fail on main.

Verification against main:

• A cmark-gfm structural oracle over 30k documents found no change in block structure.
• A placeholder-count and round-trip corpus of 340k documents found no new problem and fixed 1 round-trip failure.
• The final review's crafted sweep of 668k documents, compared against main and cmark-gfm, found 0 regressions and 483 newly fixed structures.
• The line fuzz is clean, and spec-corpus diagnostics are identical to main.

2. #83 follow-ups

Line numbers. A custom field written with spaces around its key (' tax ': ...) is now reported on its own line.

• The validator looks the key up as written (Locator.children). What is read into the model is unchanged.
• A field merged into a party (<<) has no key of its own, and the model reads merged fields first. The final review found that the pairing then gave a merged field a padded key's line.
• The source map now records a mapping's merge (positions.MERGE). Where a party merges keys in, a label that several fields share is looked up by its label, as on main.

Tests:

• a padded key;
• a padded key and a plain key together;
• a padded field name that stays ignored;
• unchanged lines for plain keys and the list form;
• a merged field next to a padded key.

README: a party key named custom_fields is reserved for the list form. The paragraph is reflowed.

Cleanup: removes w_mn.log, a stray fuzzing log that #72 committed.

3. Prepare release 0.3.0

__version__ and the README's validator_version example become 0.3.0. The LegalDown specification version stays at 0.2 everywhere: SPEC_VERSION, legaldown_spec, "Targets specification v0.2", CONFORMANCE and CI.

Release notes for the GitHub release are drafted separately. They are not in the repository, and the final review's corrections are applied to them.

Verification

The full suite passes (1942 passed, 40 skipped), and ruff is clean.

🤖 Generated with Claude Code

https://claude.ai/code/session_012pWb8FGHgaM3ZWbzsPiKsk