fix(opencode): load global rules by renaming RULES.md to AGENTS.md

RULES.md was not an opencode-recognized rules filename, so global
rules (including the "no AI co-author" Git rule) were never loaded;
only the stale, un-version-controlled ~/.claude/CLAUDE.md fallback
applied, which lacked that rule. Rename to AGENTS.md so opencode
loads it natively as the global rules file.

Also add watcher.ignore for node_modules/.git/dist/.venv/target dirs.

.claude/CLAUDE.md

@@ -0,0 +1 @@
+../.config/opencode/AGENTS.md

.config/opencode/opencode.jsonc

@@ -112,6 +112,9 @@
       },
     },
   },
+  "watcher": {
+    "ignore": ["node_modules/**", ".git/**", "dist/**", "**/.venv/**", "**/target/**"],
+  },
   "lsp": true,
   "formatter": true,
   "model": "zai-coding-plan/glm-5.2",