refactor(mcp): split claude launch-config layer into mcp_config.rs

CLAUDE.md

@@ -34,9 +34,10 @@ hand-maintained per-file tree drifts out of sync with the code.
   operator dashboard (`dashboard.rs`). Largest crate.
 - **`hive-ag3nt/`** — in-container harness; one `hive` binary for every
   agent. Turn-loop *policy* layer (`turn.rs`) over the `hive-claude`
-  driver, embedded MCP server (`mcp.rs`), per-agent web UI (`web_ui/`
-  module dir), event + turn-stats sqlite sinks, login flow, system-prompt
-  renderer, forge-notify subscriber.
+  driver, embedded MCP server (`mcp.rs`) + its claude launch-config layer
+  (`mcp_config.rs`: tool-group/capability → `--allowedTools`, `--mcp-config`
+  render), per-agent web UI (`web_ui/` module dir), event + turn-stats
+  sqlite sinks, login flow, system-prompt renderer, forge-notify subscriber.
 - **`hive-claude/`** — reusable, app-agnostic driver for headless
   `claude --print`: spawns the CLI, streams + classifies stream-json,
   parses per-turn `Telemetry`, and drives a durable self-compacting