feat: intégration plugin Kirby SEO

- Ajout de tobimori/kirby-seo via Composer
- snippet('seo/head') dans header.php (remplace les meta manuels)
- snippet('seo/schemas') dans footer.php pour JSON-LD
- Onglet SEO ajouté dans site.yml et tous les blueprints de pages
- Configuration SEO dans config.php (sitemap, robots, canonicalBase TODO)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

site/plugins/kirby-seo/docs/2_customization/06_ai-assist.md

@@ -0,0 +1,134 @@
+---
+title: Customizing AI Assist
+intro: Override prompts or add your own AI provider
+---
+
+## Overriding prompts
+
+AI Assist uses Kirby snippets for its prompts. You can override any of them by creating a snippet with the same path in your project.
+
+The built-in prompt snippets are:
+
+- `seo/prompts/tasks/title` - Meta title generation
+- `seo/prompts/tasks/description` - Meta description generation
+- `seo/prompts/tasks/og-description` - Open Graph description generation
+- `seo/prompts/tasks/site-description` - Site-level meta description
+- `seo/prompts/tasks/og-site-description` - Site-level OG description
+
+To override the meta title prompt, create `site/snippets/seo/prompts/tasks/title.php` in your project. Kirby's snippet loading will pick up your version instead of the built-in one.
+
+Each prompt snippet receives these variables:
+
+- `$page` - the current page
+- `$site` - the site object
+- `$instructions` - custom instructions from the editor (if any)
+- `$edit` - the existing text when editing (if any)
+
+There are also shared snippets that the task prompts include:
+
+- `seo/prompts/introduction` - Defines the AI's role and rules
+- `seo/prompts/content` - Extracts the page content
+- `seo/prompts/meta` - Shows existing metadata for context
+
+You can override these too. Look at the built-in prompts in `site/plugins/kirby-seo/snippets/prompts/` to understand their structure before writing your own.
+
+## Adding a custom provider
+
+If you need a provider that isn't built in, you can add your own. A provider has two parts: a driver class that handles the API communication, and a config entry that registers it.
+
+Create a class that extends `tobimori\Seo\Ai\Driver`. The only method you need to implement is `stream`, which receives a prompt string and must yield `Chunk` objects as the response comes in.
+
+```php
+<?php
+
+namespace App\Ai;
+
+use Generator;
+use tobimori\Seo\Ai\Chunk;
+use tobimori\Seo\Ai\Driver;
+use tobimori\Seo\Ai\SseStream;
+
+class MyProvider extends Driver
+{
+  public function stream(string $prompt, string|null $model = null): Generator
+  {
+    $apiKey = $this->config('apiKey', required: true);
+    $model = $model ?? $this->config('model', 'default-model');
+    $endpoint = $this->config('endpoint', required: true);
+
+    $stream = new SseStream($endpoint, [
+      'Content-Type: application/json',
+      'Accept: text/event-stream',
+      "Authorization: Bearer {$apiKey}",
+    ], [
+      'model' => $model,
+      'input' => $prompt,
+      'stream' => true,
+    ], (int)$this->config('timeout', 120));
+
+    yield from $stream->stream(function (array $event): Generator {
+      $type = $event['type'] ?? null;
+
+      if ($type === 'start') {
+        yield Chunk::streamStart($event);
+      }
+
+      if ($type === 'delta') {
+        yield Chunk::textDelta($event['text'] ?? '', $event);
+      }
+
+      if ($type === 'done') {
+        yield Chunk::streamEnd($event);
+      }
+
+      if ($type === 'error') {
+        yield Chunk::error($event['message'] ?? 'Unknown error', $event);
+      }
+    });
+  }
+}
+```
+
+The driver uses `$this->config()` to read values from the provider's `config` array in `config.php`. Pass `required: true` to throw an error if a value is missing.
+
+`SseStream` is a helper class included in Kirby SEO that handles the cURL request and SSE parsing. You pass it the endpoint, headers, payload, and a mapper function that converts raw SSE events into `Chunk` objects.
+
+If your API doesn't use SSE, you can skip `SseStream` and yield chunks directly.
+
+The chunks the Panel expects, in order:
+
+1. `Chunk::streamStart()` - Signals the stream has started
+2. `Chunk::textDelta($text)` - Each piece of generated text (repeated)
+3. `Chunk::textComplete()` - The text is done
+4. `Chunk::streamEnd()` - The stream is finished
+
+If something goes wrong, yield `Chunk::error($message)` at any point.
+
+## Registering the provider
+
+Add your driver to the config and set it as the active provider:
+
+```php
+<?php
+// site/config/config.php
+
+return [
+  'tobimori.seo' => [
+    'ai' => [
+      'provider' => 'myprovider',
+      'providers' => [
+        'myprovider' => [
+          'driver' => \App\Ai\MyProvider::class,
+          'config' => [
+            'apiKey' => 'sk-...',
+            'model' => 'my-model',
+            'endpoint' => 'https://api.example.com/v1/chat',
+          ],
+        ],
+      ],
+    ],
+  ],
+];
+```
+
+See the built-in drivers in `site/plugins/kirby-seo/classes/Ai/Drivers/` for complete implementations.