refactor(gemini-cli): change agent storage from multiple files to single (#308)

* refactor(gemini-cli): change agent storage from multiple files to single concatenated file

- Update configuration to use .gemini/bmad-method/ directory instead of .gemini/agents/
- Implement new logic to concatenate all agent files into single GEMINI.md
- Add backward compatibility for existing settings.json
- Remove old agents directory and update related documentation
- Ensure all agent settings are properly loaded

* fix(ide-setup): change agent trigger symbol from @ to *

The change was made to standardize the agent trigger symbol across the system and avoid confusion with other special characters.

* docs: update gemini cli syntax and file structure

- Change agent mention syntax from @ to * in docs and config
- Update file structure documentation from .gemini/agents/ to .gemini/bmad-method/
- Add gemini cli syntax to workflow guide

* fix(ide-setup): remove redundant contextFileNames handling

docs/agentic-tools/gemini-cli-guide.md

@@ -6,23 +6,22 @@ For the complete workflow, see the [BMad Workflow Guide](../bmad-workflow-guide.
 
 When running `npx bmad-method install`, select **Gemini CLI** as your IDE. This creates:
 
-- `.gemini/agents/` directory with all agent context files
-- `.gemini/settings.json` configured to load all agents automatically
+- `.gemini/bmad-method/` directory with all agent context in GEMINI.md file
 
 ## Using BMad Agents with Gemini CLI
 
 Simply mention the agent in your prompt:
 
-- "As @dev, implement the login feature"
-- "Acting as @architect, review this system design"
-- "@sm, create the next story for our project"
+- "As \*dev, implement the login feature"
+- "Acting as \*architect, review this system design"
+- "\*sm, create the next story for our project"
 
 The Gemini CLI automatically loads the appropriate agent context.
 
 ## Gemini CLI-Specific Features
 
-- **Context files**: All agents loaded as context in `.gemini/agents/`
-- **Automatic loading**: Settings.json ensures agents are always available
+- **Context files**: All agents loaded as context in `.gemini/bmad-method/GEMINI.md`
+- **Automatic loading**: GEMINI.md ensures agents are always available
 - **Natural language**: No special syntax needed, just mention the agent
 
 ## Tips for Gemini CLI Users

docs/bmad-workflow-guide.md

@@ -111,6 +111,7 @@ Follow the SM → Dev cycle for systematic story development:
 
 - **Claude Code**: `/agent-name` (e.g., `/bmad-master`)
 - **Cursor**: `@agent-name` (e.g., `@bmad-master`)
+- **Gemini CLI**: `*agent-name` (e.g., `*bmad-master`)
 - **Windsurf**: `@agent-name` (e.g., `@bmad-master`)
 - **Trae**: `@agent-name` (e.g., `@bmad-master`)
 - **Roo Code**: Select mode from mode selector (e.g., `bmad-bmad-master`)