feat(cypher): add connected multi-alias row bindings - #1008

Superseded by _serialize_binding_ops + orient_edges path from #1008.
The binding_ops code path correctly handles undirected edges by
doubling them (fwd + rev) in EdgeSemantics.orient_edges.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Superseded by _serialize_binding_ops + orient_edges path from #1008.
The binding_ops code path correctly handles undirected edges by
doubling them (fwd + rev) in EdgeSemantics.orient_edges.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

…stence parser (#994, #997, #998) (#1009)

* fix(cypher): handle undirected edges in bindings table (#994)

For undirected MATCH patterns, the seed node can be on either side of
the stored edge. Detect which side is the seed per-row using the src
alias boolean mask, then compute peer_id for the undirected_peer alias.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

* fix(cudf): use column check instead of .get() for cudf compat

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

* test(cypher): add undirected incoming/outgoing/bidirectional tests (#994)

3 new tests for the undirected MATCH bindings table fix:
- incoming edge returns peer not seed
- outgoing edge still correct (regression)
- bidirectional edges both return peer

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

* feat(cypher): parse shortestPath + pattern existence with clear fail-fast (#997, #998)

- shortestPath((a)-[:R*]-(b)) and allShortestPaths() now parse and
  raise GFQLValidationError("not yet supported") instead of
  GFQLSyntaxError("Invalid Cypher query syntax")
- not((a)-[:R]-(b)), exists { ... }, not exists { ... } pattern
  existence expressions now detected pre-parse and raise clear
  GFQLValidationError instead of generic syntax error

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

* test+docs(cypher): add tests for #997/#998 fail-fast, update changelog

6 new tests: 3 for shortestPath/allShortestPaths rejection,
3 for pattern existence expression rejection.
Changelog updated with #994 fix + #997/#998 parser improvements.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

* chore: retrigger CI after tck-gfql main fix

* chore: retrigger CI (tck-gfql match5-21..24 removed from xfail map)

* test(cypher): amplify #994/#998 edge case coverage

Add 4 tests: undirected with multiple edges to same nodes,
undirected star graph with multiple peers, undirected self-loop,
and pattern existence in WHERE clause.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

* refactor(lowering): remove dead _build_alias_endpoints function

Superseded by _serialize_binding_ops + orient_edges path from #1008.
The binding_ops code path correctly handles undirected edges by
doubling them (fwd + rev) in EdgeSemantics.orient_edges.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

* refactor(pipeline): remove unused undirected peer logic from alias_endpoints path

The alias_endpoints code path in _gfql_bindings_row_table is not called
from the Cypher lowering (which uses binding_ops + orient_edges instead).
The undirected seed/peer detection was added for #994 but never wired up.
Revert to the simpler src/dst join that matches the actual usage.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

* docs(changelog): fix #994 description to match actual implementation

The fix uses orient_edges (both-direction doubling), not the removed
alias_endpoints seed/peer detection approach.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

* test(cypher): add regression test for parameterized LIMIT in reentry

Covers 992f2fc fix where ParameterRef in LIMIT clause would crash
_literal_limit_value. Verifies WITH...ORDER BY...LIMIT $n...MATCH
reentry is properly rejected with a clear validation error.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

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Co-authored-by: Claude Opus 4.6 (1M context) <[email protected]>