Merge remote-tracking branch 'origin/master' into codex/trim-ai-prose

# Conflicts:
#	docs/AGENTS.md
#	docs/config-catalog.md
#	packages/bash/bash-sandbox/src/index.ts
#	packages/bash/bash/src/session-mode.ts
#	packages/bash/tool-bash/README.md
#	packages/code-runtime/code-runtime-worker/README.md
#	packages/compact/compact/src/index.ts
#	packages/core/agent-core/README.md
#	packages/hooks/hooks-claude/src/config.ts
#	packages/hooks/hooks-claude/src/index.ts
#	packages/hooks/hooks-codex/src/config.ts
#	packages/hooks/hooks-codex/src/index.ts
#	packages/llm/llm/README.md
#	packages/session-persistence/session-persistence-jsonl/README.md
#	packages/session-persistence/session-persistence/README.md
#	packages/skill/skill-local/README.md
#	packages/support/acp-snapshot/README.md
#	packages/support/invariants/src/index.ts
#	packages/ui/acp/README.md
#	packages/ui/jsonrpc-agent/README.md
#	packages/ui/jsonrpc/README.md
#	packages/ui/permission/README.md
#	packages/ui/user-approval/README.md
#	packages/ui/user-interaction/README.md
#	packages/web/web-search-deepseek/README.md

packages/subagent/subagent/README.md

@@ -59,3 +59,12 @@ Provider additions and removals also emit `subagent/provider-added` and `subagen
 ## Collection model
 
 The current model-facing tool collects synchronously: it awaits the child result and disposes the run before returning. Background collection and polling remain outside this seam. See the [capability-seam RFC](../../../docs/rfc/implemented/feature/2026-06-21-subagent-capability-seam.md) and `src/types.ts` for the complete contracts.
+
+## Model Experience
+
+Indirectly, through `dsh-tool-subagent`, which retains only a provider's data-dependent final output or exact `Error: no subagent provider registered for "<name>"`, `Error: subagent provider "<name>" does not support the "<capability>" capability`, and `Error: <message>` start failures in the parent while child working tokens remain child-only.
+
+## Known Limitations and Deferred Work
+
+- **The current consumer collects synchronously** — the model-facing tool starts a run and awaits `result`; steering (`sendMessage`) is part of the seam but intentionally unused, and background/poll/spill semantics are deferred to a future long-running-runtime design.
+- **The lifecycle events are observe-only** — a run-affecting `subagent/end` continuation or decision surface is deferred until a consumer needs one.