Emit StreamEndEvent when calling tools & reaching max steps

[GALCF]

Description

Hi prism! Great package, I love the way you structured so many providers into one approachable framework.

I recently discovered that when streaming text, tool calls - combined with a low max steps value - do not respond with a StreamEndEvent.
This is problematic in my case because only the StreamEndEvent tracks usage data.

I adapted all providers to send a StreamEndEvent when reaching max steps.
It seems DeepSeek, Groq, Mistral and XAI handled tool calls diffently, they threw "Maximum tool call chain depth exceeded" instead of stopping gracefully.
I adapted those as well and wrote tests for all providers, but I only have access to test Anthropic, Gemini, Ollama, OpenAI and Mistral with real credentials.

Feel free to ask questions, make or request changes.

Test code

I tested real credentials with the code below

$events = \prism()
    ->text()
    ->using('provider', 'model')
    ->withPrompt('First, add 2+2. Next add 3+5. Finally, add the two results together.')
    ->withTools([
        Tool::as('adder')
            ->for('Adds two numbers together.')
            ->withNumberParameter('first', 'The first number to add.')
            ->withNumberParameter('second', 'The second number to add.')
            ->using(static fn (float $first, float $second) => (string) ($first + $second)),
    ])
    ->withMaxSteps(1)
    ->withToolChoice('adder')
    ->asStream()
;

foreach ($events as $event) {
    echo $event::class . '<br>';
    \ob_flush();
    \flush();
}

Results

OpenAI (gpt-4.1-mini):

Prism\Prism\Streaming\Events\StreamStartEvent
Prism\Prism\Streaming\Events\StepStartEvent
Prism\Prism\Streaming\Events\ToolCallDeltaEvent (x9)
Prism\Prism\Streaming\Events\ToolCallEvent
Prism\Prism\Streaming\Events\ToolResultEvent
Prism\Prism\Streaming\Events\StepFinishEvent
> No StreamEndEvent

Gemini (gemini-2.5-flash):

Prism\Prism\Streaming\Events\StreamStartEvent
Prism\Prism\Streaming\Events\StepStartEvent
Prism\Prism\Streaming\Events\ToolCallEvent
Prism\Prism\Streaming\Events\ToolResultEvent
Prism\Prism\Streaming\Events\StepFinishEvent
> No StreamEndEvent

Anthropic (claude-haiku-4-5-20251001):

Prism\Prism\Streaming\Events\StreamStartEvent
Prism\Prism\Streaming\Events\StepStartEvent
Prism\Prism\Streaming\Events\ToolCallDeltaEvent (x6)
Prism\Prism\Streaming\Events\ToolCallEvent
Prism\Prism\Streaming\Events\ToolCallDeltaEvent (x7)
Prism\Prism\Streaming\Events\ToolCallEvent
Prism\Prism\Streaming\Events\ToolResultEvent (x2)
Prism\Prism\Streaming\Events\StepFinishEvent
> No StreamEndEvent

Mistral (via Google Vertex AI) (mistral-small-2503):

Prism\Prism\Streaming\Events\StreamStartEvent
Prism\Prism\Streaming\Events\StepStartEvent
Prism\Prism\Streaming\Events\ToolCallEvent (x2)
Prism\Prism\Streaming\Events\ToolResultEvent (x2)
Prism\Prism\Streaming\Events\StepFinishEvent
> PrismException: Maximum tool call chain depth exceeded

Breaking Changes

Text Streaming now emits StreamEndEvent after StepFinishEvent of tool calls