Chore: remove serena MCP completely; gitea auto-push + test-count conventions

Serena dropped from .mcp.json + .serena/ untracked (unused in practice,
flaky on Unity per CLAUDE.md's own caveat); memory stack is now three
layers. Standing auths recorded in the skill: docs auto-commit + auto-push
main->gitea (origin stays ask-first).

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

.mcp.json

@@ -3,15 +3,6 @@
     "basic-memory": {
       "command": "uvx",
       "args": ["basic-memory", "mcp"]
-    },
-    "serena": {
-      "command": "uvx",
-      "args": [
-        "--from", "git+https://github.com/oraios/serena",
-        "serena", "start-mcp-server",
-        "--context", "ide-assistant",
-        "--project", "${CLAUDE_PROJECT_DIR}"
-      ]
     }
   }
 }