Adds the docs gaps that were left when several CP changes landed without
SDK-side coverage:
- "What this is / what this isn't" callout — distinguishes molecule_agent
(outside-workspace client SDK) from molecule-ai-workspace-runtime
(in-workspace runtime), with strong forward-pointer to the runtime docs
- Channel envelope (wire format) — including the three enrichment fields
added 2026-05-02 (peer_name, peer_role, agent_card_url)
- A2A reply transport table — explicit /notify vs /a2a routing per source
- Limitations & roadmap — names the SDK gaps so follow-up issues/PRs
are trivial to file:
* fetch_inbound() missing peer_id + before_ts filters (CP PRs #2472, #2476)
* InboundMessage missing typed peer_name/peer_role/agent_card_url
* RemoteAgentClient does not auto-inject X-Molecule-Org-Id + Origin
(with a session-based workaround)
Docs-only — no Python code touched. Code work for the named gaps is
deferred to follow-up PRs so reviewers can land docs first.
hongming