Support per-directory MCP configuration in dialectic test runner

[nikomatsakis]

Enhancement: Flexible MCP Configuration

Currently dialectic has hardcoded MCP server configuration. We should extend it to support per-test-directory configuration.

Proposed approach:

• Test directories can include an optional mcp-config.json file
• This file specifies which MCP servers to load and their configurations
• Dialectic automatically loads and uses this config when running tests in that directory

Example directory structure:

dialectic/tests/memory-basic/
├── .memories/
├── mcp-config.json
└── natural-phrases-test.yaml

Example mcp-config.json:

{
  "servers": {
    "socratic-shell": {
      "command": "python",
      "args": ["-m", "socratic_shell"],
      "env": {"SOCRATIC_SHELL_LOG": "/tmp/memory-debug.log"}
    }
  },
  "allowed_tools": ["mcp__socratic-shell__read_in"]
}

Benefits:

• Tests can specify exactly which tools/servers they need
• No hardcoded assumptions about available MCP servers
• Easy to test different MCP configurations
• Cleaner separation of test concerns

Current workaround: Hardcode memory bank server in dialectic runner for memory tests.