Introduce `docs/terminology.md` with the canonical vocabulary coding
agents should use across docs, code, comments, CLI strings, and error
messages — including the disambiguation rule for the overloaded word
`source` (semantic / primary / context / source of truth) and a
converged-vs-banned table covering connectors, ingest modes, MCP
naming, reconciliation, and supported-system orderings. Reference the
new file from the `Product Naming` section of AGENTS.md so Claude,
Codex, and Gemini all pick it up via the existing AGENTS.md symlinks.
