feat: introduce workflow management tools and commands

- Added new workflow commands: `/workflow` to open the workflow panel and `/workflow run <prompt>` to execute workflows.
- Implemented `spawn_agents` and `spawn_pipeline` tools for parallel and sequential task execution, respectively.
- Enhanced workflow engine to handle real-time agent status updates and display in the UI.
- Updated workflow panel to show agent statuses, findings count, and session counters.
- Refactored existing code to integrate new workflow functionalities and improve overall structure.

src-misc/system-tools.txt

@@ -37,10 +37,17 @@ Memory & Planning:
 - todowrite(task) — Append a task to the session todo list.
 - todofinish(task_index?) — Mark a task (or all if omitted) as finished in todo.md.
 
-Workflow:
-- workflow_run(script, args) — Fan out work to sub-agents. Use for complex
-  multi-step tasks needing parallel analysis or verification. Pass inline
-  scripts with agent(), parallel(), and pipeline() primitives.
+Workflow (USE THESE AUTOMATICALLY for multi-part tasks — no user prompt needed):
+- spawn_agents(agents, max_concurrency?) — Run a list of prompts as PARALLEL subagents.
+  Each agent is fully autonomous with all tools. Returns combined results.
+  USE THIS when tasks are independent of each other.
+  Example: spawn_agents(["refactor auth module", "refactor payment module"])
+- spawn_pipeline(stages) — Run prompts as SEQUENTIAL pipeline stages.
+  Each stage can call note_finding() to pass data to later stages.
+  USE THIS when stage N needs output from stage N-1.
+  Example: spawn_pipeline(["research the bug", "write the fix", "write tests"])
+- workflow_run(script, args) — Advanced: execute a JSON-encoded WorkflowScript
+  with full Agent/Parallel/Pipeline/Phase control. Prefer spawn_agents/spawn_pipeline.
 - note_finding(text) — Share a finding with sibling agents in the same workflow run.
 
 Language Server Protocol (LSP) tools: