feat: align Go SDK with TypeScript SDK feature parity

feat: add Provider field to agent.Options for explicit provider selection

feat: OpenAI-compatible API support (GPT, DeepSeek, Ollama, OpenRouter, etc.)

Merge pull request #1 from StelloJae/feat/port-missing-tools

feat: built-in subagent spawning + AgentTool auto-registration

feat: register all new tools in GetAllBaseTools

feat: add LSP tool (grep-based fallback)

feat: add ListMcpResources and ReadMcpResource tools

feat: add EnterWorktree and ExitWorktree tools

fix: notebookedit cell_type default and negative index guard

feat: add NotebookEdit tool

feat: add CronCreate, CronDelete, CronList, RemoteTrigger tools

fix: remove redundant atomic in TeamStore, unexport PlanModeState fields

feat: add EnterPlanMode and ExitPlanMode tools

feat: add TeamCreate and TeamDelete tools