docs: add guide for venv usage

[Aadish01]

Update Troubleshooting Guide for Virtual Environment Usage

Summary

This PR enhances the troubleshooting documentation by adding guidance for users working with Python virtual environments and MCP configuration.

Changes

• Added a new section explaining issues when switching to or using a virtual environment after running code-review-graph install

• Documented that .claude/settings.json and .mcp.json contain hardcoded paths determined at install time

• Provided two resolution approaches:

  • Manually updating paths in configuration files
  • Re-running code-review-graph install within the active virtual environment

• Included an example configuration snippet for clarity

• Renumbered the subsequent troubleshooting section accordingly

Rationale

Users working with virtual environments may encounter silent failures due to outdated interpreter paths in MCP and hook configurations. This addition clarifies the root cause and provides actionable fixes, reducing setup friction.

Impact

• Documentation-only change
• Improves developer experience for users leveraging virtual environments
• No impact on runtime behavior or existing functionality

Testing

No tests required as this is a documentation update.

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