fix: issue-triage quick wins (extraction, MCP probes, gitignore, CJK, impact) (#654)

Batch of small, localized fixes from an open-issue triage:

- .codegraph/.gitignore now ignores everything but itself, so the database,
  daemon.pid, sockets, and logs stop showing up in git status (#492, #484)
- MCP server answers resources/list and prompts/list with empty lists instead
  of -32601, clearing scary log lines in opencode/Codex (#621)
- index SAP HANA .xsjs/.xsjslib as JavaScript (#556) and TS .mts/.cts (#366)
- visit anonymous AMD/CommonJS/IIFE wrapper bodies so their inner functions and
  calls are indexed instead of coming up empty (#528)
- batch the changed-file lookup so a huge first sync no longer hits
  "too many SQL variables" (#540)
- list files with `git ls-files -z` so non-ASCII/CJK paths survive
  core.quotepath and are no longer silently skipped (#541)
- attach Go methods on generic receivers (*T[P]) to their type (#583, RC1)
- impact no longer climbs the structural `contains` edge, so a leaf symbol
  stops dragging in its sibling methods (#536)
- README: explicit `codegraph install` step, run in a new shell (#631)

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

__tests__/graph.test.ts

@@ -309,6 +309,19 @@ export { main };
       expect(impact.nodes.size).toBeGreaterThan(0);
       expect(impact.nodes.has(formatValue.id)).toBe(true);
     });
+
+    it('does not drag in sibling members via the structural contains edge (#536)', () => {
+      const getName = cg.getNodesByKind('method').find((n) => n.name === 'getName');
+      const derived = cg.getNodesByKind('class').find((n) => n.name === 'DerivedClass');
+      expect(getName).toBeDefined();
+      expect(derived).toBeDefined();
+
+      const impact = cg.getImpactRadius(getName!.id, 3);
+      // The containing class must NOT be pulled into impact just because it
+      // *contains* getName — climbing that contains edge would re-expand every
+      // sibling method and explode impact for a leaf symbol. (#536)
+      expect(impact.nodes.has(derived!.id)).toBe(false);
+    });
   });
 
   describe('findPath()', () => {