docs: propose standalone MCP access roadmap

[JarrettYan-519]

Summary

This PR adds an RFC for a standalone MCP access path and cross-agent Task State roadmap.

It is intentionally documentation-only and additive:

• adds a lightweight project glossary in CONTEXT.md
• adds docs/rfcs/0001-standalone-mcp-cross-agent-state.md
• proposes a Phase 1 MCP tool surface for get_context, memory_search, capture_turn, state_get, and state_update
• keeps OpenClaw and Hermes integrations unchanged and explicitly non-deprecated
• defers host-specific lifecycle hooks and direct long-term memory promotion

Motivation

The README roadmap already calls out portable memory across agents, frameworks, and devices. This RFC frames standalone MCP access as a low-risk first step toward that direction while preserving the existing OpenClaw and Hermes paths.

Validation

• Ran a docs-only Node check to verify both new files exist, the RFC glossary link resolves, and the RFC contains no TODO/TBD/FIXME or specific client names.
• Ran git diff --cached --check before committing.

No runtime tests were run because this PR changes documentation only.

[Maxwell-Code07]

Thanks for the detailed RFC! A standalone MCP access path is a forward-looking enhancement for cross-agent memory sharing.