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/cli/installers/lib/ide/github-copilot.js

@@ -220,6 +220,7 @@ class GitHubCopilotSetup extends BaseIdeSetup {
       'problems',
       'usages',
       'editFiles',
+      'new',
       'runCommands',
       'runTasks',
       'runTests',