Post-rename cleanup: grammar artifacts, stale OCP references, schema $id domain

[macanderson]

Problem

The OCP → Context Graph Protocol rename (#1) was done with mechanical replacement, and artifacts remain that read badly in a spec repo where writing quality is credibility:

Grammar artifacts — "an OCP …" became "an Context Graph Protocol …" in at least 7 files:

rg -n "an Context Graph Protocol" --type rust docs/

hits contextgraph-types/src/frame.rs:1, query.rs, lib.rs, contextgraph-host/src/stdio.rs, docs/index.md, docs/implementing-a-provider.md (×3), docs/protocol-advantages.md.

Double-expansion artifacts — "Open Context Protocol (OCP)" became self-referential:

• docs/protocol-advantages.md:3-4: "the Open Context Protocol (Context Graph Protocol)"
• docs/protocol-advantages.md:19-20: "The Context Graph Protocol (Context Graph Protocol)"

And a general tic worth a pass: the replacement produced heavy repetition of the four-word name mid-sentence where "CGP" or "the protocol" would read naturally (e.g. README line 77, protocol-advantages.md throughout).

Also verify while in here:

• schema/contextgraph-envelope.schema.json $id points at https://context-graph-protocol.org/… — confirm that domain is actually registered/intended, or repoint the $id at the GitHub Pages / site URL before third parties start referencing it
• site/ content and metadata for stale OCP/opencontextprotocol references (the old remote was github.com:macanderson/opencontextprotocol)
• .stella/ directory at repo root — looks like imported tooling state; confirm it's meant to be committed or gitignore it

Suggested sweep

rg -n "an Context Graph Protocol|Open Context Protocol|\bOCP\b|opencontextprotocol" --hidden -g '!target' -g '!node_modules'

Decide once whether the abbreviation is "CGP" and introduce it at first mention per document ("Context Graph Protocol (CGP)"), then use it thereafter.

Acceptance criteria

• The sweep above returns zero unintended hits
• $id domain decision recorded
• One abbreviation convention applied consistently across README + docs