fix(mcp): NAME_PREFIX regex rejects hyphenated server names like sage-wiki

[ctharvey]

Bug. The NAME_PREFIX regex in src/mcp/spec.ts uses [a-zA-Z0-9_] which excludes hyphens. The MCP ecosystem standardizes on kebab-case names, so sage-wiki=command args fails the prefix match and the entire string (including the =) gets treated as a raw command path.

Fix: add - to the character class.