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

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packages/server/.gitignore

@@ -5,3 +5,4 @@ dist
 *.log
 .debug.conversations
 conversations
+.cache