Rename mcp/setup-all-mcp-servers.sh to setup.sh

## Summary
Rename `mcp/setup-all-mcp-servers.sh` to `mcp/setup.sh` for consistency and simplicity.

## Rationale
- Follows established pattern where directories have their own `setup.sh` (like root directory)
- Directory context (`mcp/setup.sh`) makes purpose clear
- Natural entry point users would look for
- Aligns with subtraction-creates-value principle (shorter, simpler name)

## Tasks
- [ ] Rename `mcp/setup-all-mcp-servers.sh` to `mcp/setup.sh`
- [ ] Update any references in documentation or other scripts
- [ ] Test that setup still works correctly after rename

## Principle
subtraction-creates-value

Start by inspecting mcp/setup-all-mcp-servers.sh and searching the repository for references to its current name. Rename it to mcp/setup.sh, update any documented or scripted references, and verify that the setup process still works.

Written by the indexing model from the issue text.