refactor: remove terminal MCP, Playwright, and commands infrastructure

- Remove terminal/tmux MCP from voice LLM - it now only uses agent-control MCP
- Remove Playwright MCP auto-injection from Claude and Codex agents
- Remove commands state from session, store, and UI
- Remove present_artifact tool and guidelines from voice prompt
- Update agent-prompt.md examples to focus on agents instead of commands
- Remove @huggingface/transformers dependency and test scripts
- Add expandTilde utility to utils/path.ts

🤖 Generated with [Claude Code](https://claude.com/claude-code)

packages/server/src/utils/path.ts

@@ -0,0 +1,15 @@
+import os from "os";
+
+/**
+ * Expand tilde in path to home directory
+ */
+export function expandTilde(path: string): string {
+  if (path.startsWith("~/")) {
+    const homeDir = process.env.HOME || os.homedir();
+    return path.replace("~", homeDir);
+  }
+  if (path === "~") {
+    return process.env.HOME || os.homedir();
+  }
+  return path;
+}