Merge remote-tracking branch 'origin/master' into jsonl-packed-chunk-rows

Master's Zstandard physical encoding (#416) and this branch's packed chunk
rows compose as orthogonal layers: packChunks shapes the logical storage
records, compression shapes the physical bytes. The backend keeps both
config keys; eventLines(events, packChunks) replaces master's singular
eventLine helper and feeds encodeMaterialization/encodeEventBatch so packed
rows flow through either encoding. Demo apps carry both passthroughs. The
packed-row layout tests pin compression: 'none' (they assert textual line
tags) and read through rawLogPath; zstd spec fixtures inline
JSON.stringify for verbatim lines.

packages/examples/acp-demo/README.md

@@ -38,6 +38,7 @@ Because the package wires no logger entry, an ACP leaf has **nothing to get wron
 | `toolTasks` | owner defaults | generic `task_output` wait bounds routed through `dsh-agent-spine-demo` |
 | `persistenceRoot` | `./.sessions` | the JSONL backend's root directory |
 | `packChunks` | `false` | write delta-chunk runs as packed storage rows (the JSONL backend's `packChunks`) |
+| `persistenceCompression` | `'zstd'` | JSONL artifact encoding (`'zstd'` or raw `'none'`) |
 
 The leaf supplies the swappable backends: an LLM adapter (`llm-deepseek` for the real model, `llm-replay` for keyless snapshot replay), a bash executor, and optionally a `ctx.fs` provider. Workspace context becomes a no-op without `ctx.fs`; the shipped [`examples/acp-agent/cordis.yml`](../../../examples/acp-agent/cordis.yml) selects `dsh-sandbox-policy`, `dsh-fs-sandbox`, `dsh-fs-policy`, and `dsh-tool-fs` so baseline instructions and model-facing `read`/`write`/`edit` share one provider, sandbox mode, workspace root, and observed-version policy.