Fix chained predicates on ancestor axis

[mislav]

The XPath expression with chained predicates on the ancestor axis was not working correctly. For example:

//*[@itemprop="author"][ancestor::*[@itemscope][1][@itemtype="Comment"]]

This expression should find all elements with @itemprop="author" whose first @itemscope ancestor has @itemtype="Comment". However, it was returning 0 results instead of the expected elements.

Root cause:

1. ancestorQuery.table (deduplication table) was persisting across Evaluate() calls, preventing ancestors from being found for subsequent input contexts.
2. filterQuery.positmap (position map) was not being reset during Evaluate(), causing position tracking to be incorrect when the same predicate query was reused for multiple input nodes.

Fix:

• Reset ancestorQuery.table to nil in Evaluate() to ensure clean state for each evaluation
• Reset filterQuery.positmap to nil in Evaluate() to ensure clean state for each evaluation

These changes ensure that when a predicate query is evaluated multiple times (once for each candidate node), the internal state is properly reset, allowing the query to work correctly for each evaluation.

💁 Unit test by Mislav
🤖 Implementation by Claude Code

[coveralls]

coverage: 78.01% (+0.03%) from 77.98%
when pulling 02c01b0 on mislav:fix-ancestor-predicate-chain
into 511abd5 on antchfx:master.