Feature/add ai collector

[NielsSmits1]

Add AiCollector for laravel/ai agent runs

Adds an AiCollector (and provider) that shows each laravel/ai agent invocation in the debug bar as a single entry: prompt, instructions, model/provider, tool calls and token usage. Built in the same style as the existing PennantCollector.

How it works

• One entry per invocation. ToolInvoked fires during a run and AgentPrompted at the end; tool calls are buffered by invocationId and folded into the entry recorded on AgentPrompted (AgentStreamed is handled identically).
• Guarded, zero overhead when unused. The provider only registers when Laravel\Ai\AiManager exists — apps without laravel/ai are unaffected, just like PennantCollectorProvider guards on FeatureManager.
• No new front-end assets. Reuses the existing JsonVariableListWidget / HtmlVariableListWidget / VariableListWidget, chosen the same way as SessionCollector / RouteCollector.
• Kept lean. Prompt/response/tool bodies are truncated at 20k chars; attachments are counted only.

Configuration

'collectors' => [
    'ai' => env('DEBUGBAR_COLLECTORS_AI', true),
],
'options' => [
    'ai' => [
        'values' => env('DEBUGBAR_OPTIONS_AI_VALUES', true), // Collect prompt/response/tool bodies
    ],
],

Set 'values' => false for metadata only (agent, model, provider, usage, attachment count), handy when prompts are sensitive or large. laravel/ai is added to require-dev only — never a hard require.

Tests

AiCollectorTest (5 tests): provider registration, folding tool calls into the matching invocation, per-invocation buffer consumption, the values toggle, and truncation.

Caveat

Debugbar captures data per HTTP request, so you only see AI runs for synchronous calls (QUEUE_CONNECTION=sync or inline); for queued jobs a Telescope watcher fits better.