fix(cypher): MATCH returns all matching rows (Issue #269)

[aepod]

Summary

Fixes #269 — MATCH (n:Person) RETURN n now correctly returns all matching rows instead of only the last one.

Root Cause

execute_match() collapsed all match results into a single ExecutionContext via context.bind(), which overwrites previous bindings in a HashMap. Three matches → only the last survived into execute_return(), producing 1 row.

Fix

Refactored the executor to use a ResultSet pipeline (Vec<ExecutionContext>):

• Each clause transforms ResultSet → ResultSet
• execute_match() expands the set (one context per match)
• execute_return() projects one output row per context
• execute_set/delete() apply to all contexts in the set
• Cross-product semantics for multiple patterns in a single MATCH

Tests Added

Test	What it verifies
test_match_returns_multiple_rows	3 Person nodes → 3 rows (the #269 regression)
test_match_return_properties	Correct property values per row (Alice, Bob)
test_match_where_filter	WHERE correctly filters multi-row results
test_match_single_result	1 match → 1 row (no regression)
test_match_no_results	0 matches → 0 rows
test_match_many_nodes	100 nodes → 100 rows (stress test)

Files Changed

• crates/rvlite/src/cypher/executor.rs — Core fix: ResultSet pipeline
• crates/rvlite/src/cypher/mod.rs — 6 new tests

🤖 Generated with claude-flow

[aepod]

test result: ok. 30 passed; 0 failed; 2 ignored

Key results:

• test_match_returns_multiple_rows — PASS (was the Issue CypherEngine: MATCH RETURN produces single row — context.bind() overwrites previous bindings #269 bug)
• test_match_return_properties — PASS (Alice + Bob both returned)
• test_match_where_filter — PASS (WHERE correctly filters multi-row)
• test_match_many_nodes — PASS (100 nodes → 100 rows)
• All existing tests — PASS (no regressions)