test(cortex-cli): add comprehensive unit tests for CLI modules (#550)

Add unit tests across multiple cortex-cli modules to increase code coverage:

- Command modules: acp_cmd, agent_cmd, alias_cmd, cache_cmd, compact_cmd,
  debug_cmd, feedback_cmd, lock_cmd, logs_cmd, mcp_cmd, models_cmd,
  plugin_cmd, shell_cmd, workspace_cmd
- Core: lib.rs, cli/args, cli/handlers, completion_setup
- Utilities: file, paths, session, wsl_paths
- MCP: config, handlers, types, validation
- Exec: jsonrpc

Tests cover struct initialization, serialization/deserialization,
validation logic, edge cases, and error handling.

Author: echobt

Cargo.lock

@@ -87,3 +87,4 @@ chrono = "0.4"
 
 [dev-dependencies]
 serial_test = { workspace = true }
+tempfile = { workspace = true }