refactor(examples): rename coding-agent leaf to repl-agent

Name the runnable leaf for the line-oriented front door it owns, matching the existing tui-agent and acp-agent organization. Move the complete config, Code Mode overlay, tests, metadata, and generated composition graph together, then update every loader path and repository reference.

Keep the shared model identity independent of its terminal front door by phrasing the persona as a coding-agent role rather than retaining the retired leaf name. Regenerate graph and tool catalogs and re-record each affected bilingual pair so derived documentation cannot point at the removed path.

examples/echo-agent/README.md

@@ -9,7 +9,7 @@ This example is just a leaf `cordis.yml`: it loads the [`@deepseek-ai/dsh-stdio-
 - `mock-llm.ts` — a mock `LlmAdapter` that streams scripted responses and calls the `echo` tool when the user types "echo <something>". Registered with `ctx.llm.registerAdapter(['mock-echo'], …)`.
 - `echo-tool.ts` — a tool registered via `ctx.tools.register(defineTool(…))` with typed `execute` args; echoes text back uppercased.
 
-Swapping `mock-llm` for the real `llm-deepseek` adapter is all that separates this from `coding-agent` — the same app, a different backend.
+Swapping `mock-llm` for the real `llm-deepseek` adapter is all that separates this from `repl-agent` — the same app, a different backend.
 
 ## Plugin files