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>

src/extraction/languages/go.ts

@@ -56,8 +56,12 @@ export const goExtractor: LanguageExtractor = {
     if (!receiver) return undefined;
     // Find the type identifier inside the receiver
     const text = getNodeText(receiver, source);
-    // Extract type name from patterns like "(sl *Type)", "(sl Type)", "(*Type)", "(Type)"
-    const match = text.match(/\*?\s*([A-Za-z_][A-Za-z0-9_]*)\s*\)/);
+    // Extract type name from "(sl *Type)", "(sl Type)", "(*Type)", "(Type)" and
+    // generic receivers "(s *Stack[T])". Anchor on the opening "(" and skip an
+    // optional receiver var name; the old `name)`-anchored pattern never matched
+    // the `[T])` suffix, so generic-type methods were orphaned from their type
+    // (no struct→method `contains` edge). (#583)
+    const match = text.match(/\(\s*(?:[A-Za-z_]\w*\s+)?\*?\s*([A-Za-z_]\w*)/);
     return match?.[1];
   },
 };