[JayPokale]

Closes #117

In a MATCH with several comma-separated patterns, LogicalPlanner::plan_path always continued a later path from the plan built so far, even when the path's start node is a variable that no earlier pattern bound. That start node was never scanned. For the query in #117 the logical plan was:

Filter
  Expand p -> h          <- p was never scanned
    Expand p -> c
      Expand c -> co
        ScanByLabel c

so the columns of p, and of nodes reached from it, were missing. On main the query from the issue fails with Failed to build filter: Schema error: No field named h__name, and the simpler

MATCH (c:City)-[:inCountry]->(co:Country), (p:Person)-[:livesIn]->(c)
WHERE co.name = 'France' RETURN p.id AS id

fails with No field named p__id.

The fix: when a later path starts at an unbound variable (or an anonymous node), plan a ScanByLabel for it and join it with the plan so far. As before, a path that starts at an already-bound variable continues from the plan. When the path then reaches an already-bound node (c above), the existing variable-reuse filter in join_relationship_to_target connects the two patterns, so the result is correct. The join is a cross join followed by that filter; a join on the relationship could be planned more cheaply, but I kept this change to fixing correctness.

Tests (tests/test_multi_match_where.rs), run on the DataFusion executor with three people, two cities, two countries and two hobbies:

• the query from Multi-match query with WHERE predicate downstream filter/projection fails #117: returns only the person in France who plays chess (fails on main);
• a second pattern that starts at a new variable p: returns both people in France (fails on main);
• a filter on aliases from each of two patterns sharing p (already passed; kept as coverage).

Commands run in crates/lance-graph: cargo test (all unit, integration and doc tests pass), cargo fmt --all -- --check, cargo clippy --all-targets -- -D warnings.

I used an AI assistant (Claude) while working on this; I reviewed and tested the change.