Why: D46/D47 approved — artifact_ref parts left only a name line in model
context (next-turn amnesia on big tool results), and artifacts had no
inbox presence unlike submit_card products.
Evidence: ctxasm ArtifactResolver backfills UTF-8 artifact text with the
card char limit (Truncations + artifact(n) observable; binary keeps
placeholder); runmgr runCtx.Artifact; llm.go auto-creates a result facade
card (summary kv + doc-ref) when a tool result is truncated, suppressed
when the run already submitted an explicit card; mock #doc demos the
facade; new tests TestAssembleInputArtifactBackfill,
TestLLMRunnerArtifactFacadeCard/Suppressed, e2e TestArtifactFacadeCard.
Impact: frontend unchanged — artifact chips and doc-ref already resolve
via docBridge; no wire protocol change.
Refs: documents proposal 2026-09-30-card-stream-artifact-unify-project-inbox.md (D46/D47).
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