TOTAL_MCP_TOOL_COUNT in open-sse/mcp-server/server.ts summed collection sizes
additively, double-counting tools registered in more than one collection.
The agent-skills trio (omniroute_agent_skills_list/get/coverage) is
intentionally defined in both MCP_TOOLS (schemas/tools.ts) and
agentSkillTools (tools/agentSkillTools.ts), inflating the reported count
from 96 unique tools to 99.
Replace the additive sum with countUniqueMcpTools() (new
open-sse/mcp-server/toolCount.ts), which unions all collection tool
names into a Set before counting, so any future overlap self-corrects
instead of double-counting.
Regression test: tests/unit/mcp-tool-count-dedup-6854.test.ts
