Add 'new' tool to GitHub Copilot chatmodes for file creation

Fixes #505 - GitHub Copilot analyst chat mode is unable to create files

- Added 'new' tool to tools array in setupGitHubCopilot() method
- Enables file creation capability for all BMAD chatmode agents
- Follows pattern from PR #324 (commit 47b014e)
- Based on research showing 'editFiles' alone insufficient for new files

Research evidence:
- Issue #12568 in microsoft/vscode-copilot-release shows 'new' as distinct tool
- Issue #10253 documents editFiles limitation with creating non-existent files
- Microsoft fixed file creation bug in extension v0.28.2025052204+

Testing required:
- Run BMAD installer to regenerate chatmode files
- Test analyst agent commands: *create-project-brief, *create-competitor-analysis
- Verify existing agent functionality unchanged

tools/installer/lib/ide-setup.js

@@ -2176,7 +2176,7 @@ ${taskContent}
 
         let chatmodeContent = `---
 description: "${description.replaceAll('"', String.raw`\"`)}"
-tools: ['changes', 'codebase', 'fetch', 'findTestFiles', 'githubRepo', 'problems', 'usages', 'editFiles', 'runCommands', 'runTasks', 'runTests', 'search', 'searchResults', 'terminalLastCommand', 'terminalSelection', 'testFailure']
+tools: ['changes', 'codebase', 'fetch', 'findTestFiles', 'githubRepo', 'problems', 'usages', 'editFiles', 'new', 'runCommands', 'runTasks', 'runTests', 'search', 'searchResults', 'terminalLastCommand', 'terminalSelection', 'testFailure']
 ---
 
 `;