Implement environment-specific MCP configuration

## Problem
The current MCP configuration approach causes issues when using the same `mcp.json` across different environments (work vs personal). Specifically, the Atlassian MCP server causes timeouts on personal computers while being essential for work environments.

## Proposed Solution
Implement a simple environment-specific MCP configuration system that:
1. Creates separate work and personal MCP configurations
2. Provides a simple script to switch between configurations
3. Adds bash aliases for easy switching
4. Follows the dotfiles philosophy of automation and reproducibility

## Implementation Tasks
- [ ] Create `mcp-configs` directory for storing environment-specific configurations
- [ ] Create `mcp-select.sh` utility script for switching between configurations
- [ ] Add bash aliases for easy environment switching
- [ ] Update setup script to handle the new configuration approach
- [ ] Document the new approach in README.md

This approach maintains the "spilled coffee principle" while allowing different configurations for different environments.

Start by reading the existing setup script and current MCP configuration, then inspect how README.md documents setup and where bash aliases are defined. Add the mcp-configs directory, mcp-select.sh utility, switching aliases, setup integration, and README.md guidance; done means work and personal configurations can be selected reproducibly.

Written by the indexing model from the issue text.