ci(compat): trigger Backend-Compat-Test on real graph_storage path (#1926)

The pull_request paths filter on compat-test.yml only watched
``aperag/domains/knowledge_graph/graphindex/**`` and
``aperag/vectorstore/**``, but the actual graph store backends were
moved to ``aperag/indexing/graph_storage/{neo4j,nebula,postgres}.py``.
Any PR touching those files therefore bypassed Backend-Compat-Test —
exactly the workflow that exists to catch cross-adapter regressions
(e.g. the ``GET /graphs/labels`` 500 on Neo4j vs. pass on Nebula/PG
that 冬柏 surfaced as a P0 candidate, or today's neo4j.py edits).

Add ``aperag/indexing/graph_storage/**`` to the trigger list. Keep
the legacy ``aperag/domains/knowledge_graph/graphindex/**`` entry as
a defensive fallback for any follow-up commits that still touch the
old tree.

Pure CI configuration change; no test logic, no production code.
This is task #61 P0 surfaced by chenyexuan's workflow-gate audit
slice (cite trail in #indexing优化 msg=f298011e).

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

Author: earayu

.github/workflows/compat-test.yml

@@ -4,8 +4,20 @@ on:
   pull_request:
     branches: [main]
     paths:
-      - 'aperag/domains/knowledge_graph/graphindex/**'
+      # Real graph store implementations (Neo4j / Nebula / PG).
+      # The legacy ``aperag/domains/knowledge_graph/graphindex`` tree
+      # has been gradually migrated under ``aperag/indexing/graph_storage``;
+      # without this entry, Backend-Compat-Test does NOT trigger when a
+      # PR modifies neo4j.py / nebula.py / postgres.py — exactly the
+      # invariant this workflow exists to defend.
+      - 'aperag/indexing/graph_storage/**'
+      # Vector store adapters (PGVector / Qdrant).
       - 'aperag/vectorstore/**'
+      # Legacy graphindex shim path kept as a defensive trigger; the
+      # active backend code now lives under aperag/indexing/graph_storage/
+      # but follow-up commits may still touch this tree, and removing
+      # the entry could miss those.
+      - 'aperag/domains/knowledge_graph/graphindex/**'
       - 'tests/integration/compat/**'
       - '.github/workflows/compat-test.yml'
   workflow_dispatch: