docs: add hands-on Cordis tutorial

Seven-chapter tutorial under docs/cordis-tutorial/ for agent developers
new to Cordis: first plugin, lifecycle/effects, services, events,
config, composition/HMR, and a final chapter registering a tool against
real harness services. Every transcript was produced by running the
chapter files in a gitignored tmp/ scratch directory.

Published to both website locales as mirrored English pages under a new
'Cordis tutorial' develop-sidebar section; a Chinese pair can be added
later without route changes.

docs/cordis-tutorial/07-into-the-harness.md

@@ -0,0 +1,101 @@
+# 7. Into the harness
+
+This chapter registers a model-callable tool with the harness's `tools` service, executes it through the harness tool pipeline, and observes the result event. It remains keyless and does not call a model.
+
+## A tool plugin
+
+Create `greet-tool.ts` in `tmp/cordis-tutorial`:
+
+```ts
+import type { Context } from 'cordis'
+import { defineTool } from '@deepseek-ai/dsh-tools'
+import { CallId } from '@deepseek-ai/dsh-llm'
+
+export const name = 'greet-tool'
+export const inject = ['tools']
+
+export function apply(ctx: Context) {
+  ctx.tools.register(defineTool({
+    name: 'greet',
+    description: 'Greet the named person.',
+    parameters: {
+      name: { type: 'string', required: true, description: 'Who to greet' },
+    },
+    async execute(args) {
+      return [{ type: 'text', text: `Hello, ${args.name}!` }]
+    },
+  }))
+
+  // Drive one call through the real execution pipeline, standing in for
+  // the model. CallId brands the correlation id a provider would issue.
+  void (async () => {
+    const result = await ctx.tools.execute({
+      callId: CallId('demo-1'),
+      name: 'greet',
+      arguments: { name: 'Cordis' },
+      signal: new AbortController().signal,
+    })
+    console.log('tool replied:', JSON.stringify(result.content))
+  })()
+}
+```
+
+Every pattern here is from the earlier chapters: `inject: ['tools']` ([chapter 3](03-services.md)) holds the plugin until the tool registry exists; `ctx.tools.register(...)` attaches the registration disposer to the plugin ([chapter 2](02-lifecycle-and-effects.md)), so unloading unregisters the tool. `defineTool` converts the `parameters` spec to the JSON Schema shown to the model, infers the type of `args`, and validates model-supplied arguments before `execute` runs.
+
+## An observer plugin
+
+Create `tool-logger.ts` — a separate plugin that watches every tool call in the app through the harness's `tools/result` event:
+
+```ts
+import type { Context } from 'cordis'
+import type {} from '@deepseek-ai/dsh-tools'
+
+export const name = 'tool-logger'
+export const inject = ['tools']
+
+export function apply(ctx: Context) {
+  ctx.on('tools/result', (exec, result) => {
+    const text = result.content
+      .map(block => (block.type === 'text' ? block.text : ''))
+      .join('')
+    console.log(`[tool-logger] ${exec.name} -> ${text}`)
+  })
+}
+```
+
+The `import type {} from '@deepseek-ai/dsh-tools'` line pulls in the package's declaration merges so `'tools/result'` and its payload are typed — the same move as chapter 4's `stats.ts` import, at package scale.
+
+## Compose and run
+
+```yaml
+- name: '@deepseek-ai/dsh-system-prompt'
+- name: '@deepseek-ai/dsh-tools'
+- name: './tool-logger.ts'
+- name: './greet-tool.ts'
+```
+
+`@deepseek-ai/dsh-tools` injects the `systemPrompt` service because tools contribute schemas to the system prompt, so the composition lists its provider too. Without it, the tools plugin remains PENDING as described in [chapter 6](06-composition-and-hmr.md).
+
+```sh
+node --import tsx ../../vendor/cordis/bin.js
+```
+
+```
+[tool-logger] greet -> Hello, Cordis!
+tool replied: [{"type":"text","text":"Hello, Cordis!"}]
+```
+
+The logger fired first: `tools/result` is emitted as part of result materialization, before `execute`'s promise resolves to the caller. Neither of your plugins knows the other exists — the registry service and the event connect them.
+
+## From here to a full agent
+
+A real agent is this composition plus more plugins: an LLM adapter, the agent loop, persistence, a front end. Compare [examples/headless-agent/cordis.yml](../../examples/headless-agent/cordis.yml) — you can read every entry in it now. Add your `greet-tool.ts` to a copy of that file and, with a `DEEPSEEK_API_KEY` in the root `.env`, the model can actually call your tool.
+
+Where to go next:
+
+- [Build a tool](../user/develop/basic/tool.md) — more of `defineTool`, including presentation and richer schemas.
+- [Three-layer capability design](../user/develop/practice/index.md) — how the harness structures replaceable capabilities.
+- The generated [services](../cordis-catalog/services.md) and [events](../cordis-catalog/events.md) catalogs — everything you can inject and listen to.
+- [Architecture](../architecture.md) — the system map these plugins live in.
+
+[![](https://img.shields.io/badge/powered_by-dsh-4D6BFE?style=flat-square&logo=deepseek&logoColor=white)](https://github.com/deepseek-harness/deepseek-harness)