Add GitHub issue template for bug reports

This adds a structured template for bug reports including fields for:
- Platform selection (Anthropic API, AWS Bedrock, Google Vertex AI)
- Claude CLI version information
- OS details
- Steps to reproduce

🤖 Generated with [Claude Code](https://claude.ai/code)
Co-Authored-By: Claude <noreply@anthropic.com>

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,33 @@
+---
+name: Bug report
+about: Create a report to help us improve
+title: '[BUG] '
+labels: bug
+assignees: ''
+---
+
+## Environment
+- Platform (select one):
+  - [ ] Anthropic API
+  - [ ] AWS Bedrock
+  - [ ] Google Vertex AI
+  - [ ] Other: <!-- specify -->
+- Claude CLI version: <!-- output of `claude --version` -->
+- Operating System: <!-- e.g. macOS 14.3, Windows 11, Ubuntu 22.04 -->
+
+## Bug Description
+<!-- A clear and concise description of the bug -->
+
+## Steps to Reproduce
+1. <!-- First step -->
+2. <!-- Second step -->
+3. <!-- And so on... -->
+
+## Expected Behavior
+<!-- What you expected to happen -->
+
+## Actual Behavior
+<!-- What actually happened -->
+
+## Additional Context
+<!-- Add any other context about the problem here, such as screenshots, logs, etc. -->