docs: add Phase 8C MCP design-only plan

[ProfRandom92]

Summary

Adds a docs-only Phase 8C MCP design plan for the CompText / Codex operating layer.

This PR defines review-gated MCP concepts only. It does not activate MCP, install plugins, enable hooks, register global skills, run provider/model calls, or mutate runtime/source artifacts.

Scope

Added:

• docs/PHASE8C_MCP_DESIGN_ONLY.md

Covers:

• MCP trust boundary
• read-only Git topology/diff/history MCP concept
• read-only docs/RAG MCP concept
• read-only CI/log MCP concept
• local Context Pack MCP concept
• proposal review MCP concept
• denied initial operations
• interaction with Phase 8A draft skills
• interaction with Phase 8B plugin scaffold
• claim hygiene
• artifact hygiene
• promotion gates before .mcp.json or .codex/** changes

Explicit non-goals

This PR does not:

• create .mcp.json
• edit .codex/**
• edit .agent/skills/**
• edit AGENTS.md
• edit README.md
• edit source code
• edit reports or artifacts
• install packages
• register MCP servers
• activate plugins
• activate hooks
• install global skills
• run provider/model calls
• use Computer Use
• deploy, release, merge, or rebase

Validation

Local:

• git diff --check origin/main...HEAD
• git diff --stat origin/main...HEAD
• branch status clean before push

Expected diff:

• one docs-only file
• no source/runtime/config activation

Review status

Draft PR. Keep draft until review confirms:

• MCP concepts remain read-only/design-only
• denied operations are explicit enough
• promotion gates are sufficient before any future .mcp.json, .codex/**, plugin, hook, skill, or automation activation

[gemini-code-assist]

Code Review

This pull request introduces a design-only document, docs/PHASE8C_MCP_DESIGN_ONLY.md, which outlines candidate Model Context Protocol (MCP) concepts for future CompText and sparkctl operating-layer work. The feedback identifies several hallucinated URLs pointing to developers.openai.com/codex/... and suggests replacing them with correct official sources, such as modelcontextprotocol.io and Anthropic's documentation, or internal references.

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