refactor(examples): DRY the acp-agent configs via base-core.yml + acp-tail.yml

The snapshot replay config duplicated most of base.yml + the acp tail just to
swap llm-deepseek → llm-replay. Factor the shared pieces:

- examples/base-core.yml: the providerless provider/tool core (llm, sessions,
  system-prompt, tools, agents, invariants, bash-local, tool-bash). base.yml is
  now base-core + the llm-deepseek adapter; the snapshot replay config is
  base-core + llm-replay. The replay config no longer hand-copies the core.
- examples/acp-agent/acp-tail.yml: agent-loop (no pre-created agents) +
  persistence + the ACP bridge/system-prompt, shared by cordis.yml and the
  replay config so the three acp-agent configs can't drift. Its persistence root
  is `$DSH_SNAPSHOT_SESSIONS_ROOT ?? ./.sessions`.
- Deleted cordis.snapshot-record.yml: recording now reuses the normal cordis.yml
  (real adapter), with the harness redirecting the persistence root via env.
  start.ts maps DSH_SNAPSHOT=record → cordis.yml.

Verified: snapshot replay 8/8 keyless; record path works through cordis.yml;
ACP e2e no-key boot green through the doubly-nested include (cordis.yml →
base.yml → base-core.yml); coding-agent boots clean; all gates pass.

examples/acp-agent/cordis.yml

@@ -1,4 +1,6 @@
-# The acp-agent plugin tree, loaded via @cordisjs/plugin-include.
+# The acp-agent plugin tree, loaded via @cordisjs/plugin-include. Also the
+# snapshot RECORD config (start.ts selects it for DSH_SNAPSHOT=record): a real
+# llm-deepseek run whose persisted log the snapshot harness harvests.
 #
 # CRITICAL: this example loads NO stdout logger (no @cordisjs/plugin-logger-
 # console, no stdio-chat). stdout is reserved for the ACP JSON-RPC protocol —
@@ -12,38 +14,17 @@
 - id: timer
   name: '@cordisjs/plugin-timer'
 
-# Shared provider/tool core (llm, sessions, system-prompt, tools, agents,
-# invariants, llm-deepseek, bash-local, tool-bash). Nested include resolved
-# relative to THIS file's directory.
+# Shared provider/tool core, INCLUDING the real llm-deepseek adapter. Nested
+# include resolved relative to THIS file's directory.
 - id: base
   name: '@cordisjs/plugin-include'
   config:
     path: '../base.yml'
 
-# agent-loop with NO pre-created agents: ACP `session/new` creates them on
-# demand (unlike coding-agent, which pre-creates `main`).
-- id: agent-loop
-  name: '@deepseek-ai/dsh-agent-loop'
+# agent-loop (no pre-created agents) + JSONL persistence + the ACP bridge.
+# Shared with the snapshot REPLAY config (cordis.snapshot.yml) so the three
+# acp-agent configs don't drift.
+- id: acp-tail
+  name: '@cordisjs/plugin-include'
   config:
-    agents: []
-
-# Durable session persistence — required by the ACP bridge for `session/load`.
-- id: session-persistence
-  name: '@deepseek-ai/dsh-session-persistence-jsonl'
-  config:
-    root: './.sessions'
-
-# The ACP bridge: wires AgentSideConnection to stdin/stdout.
-- id: acp
-  name: '@deepseek-ai/dsh-acp'
-  config:
-    model: deepseek-v4-flash
-    systemPrompt: |
-      You are a coding assistant driven over the Agent Client Protocol.
-
-      Your only tools are bash (plus bash_output/bash_kill for background
-      tasks). Do ALL file operations through bash: read with cat/sed/head,
-      search with grep, write with heredocs (cat <<'EOF' > file), edit with
-      sed or a rewrite. Each bash call runs in a fresh shell — pass workdir
-      instead of cd. Check the [exit code: N] marker; verify your work. Keep
-      answers brief and factual.
+    path: './acp-tail.yml'