MIP-0001 and MIP-0002 for discussion: proposal process and light client infrastructure

[christopherwxyz]

This thread is for review of the initial Makechain Improvement Proposal bootstrap:

• MIP-0001 defines the lightweight MIP process and document structure
• MIP-0002 proposes light client infrastructure changes covering proof key prefixes, validator commitments in block headers, mutable proof freshness, and finalized historical root lookup

Draft PR: #9

Earlier draft PRs were superseded during title and branch cleanup. The current proposal branch is mip/mips-bootstrap.

The goal here is to align on the proposal process first and then iterate on the protocol changes in the open.