MCP server for agent-driven control of Hance

[RichardBray]

Why

Power-user feature scoped out of #133 (Mac app). Lets users drive Hance via their own agent/harness instead of the GUI or CLI directly.

Approach

• MCP server exposing Hance's effects pipeline (grade, halation, aberration, weave) as tools - params matching CLI flags.
• Runs alongside or inside the Mac app (Mac app: native Electrobun shell for packages/ui #133) once that ships, or standalone via CLI in the meantime.
• Read-only status/progress tool for long-running exports.

Scope

• Define MCP tool schema for each effect + export
• Server implementation (stdio or local socket transport)
• Docs for connecting Claude Code / other MCP clients
• Auth/scoping if run alongside GUI app (avoid conflicting concurrent jobs)

Depends on

Not blocking - can ship standalone against current CLI, but pairs naturally with #133.