Sync with official SDK PR #346: SessionLifecycle events and headless flag

[Copilot]

Ports changes from github/copilot-sdk#346 which adds TUI+server mode support for managing sessions displayed in the Copilot CLI terminal UI.

New Types

• SessionLifecycleEventType enum: session.created, session.deleted, session.updated, session.foreground, session.background
• SessionLifecycleEvent readonly class with type, sessionId, and optional metadata
• ForegroundSessionInfo readonly class for foreground session data

Client Methods

• getForegroundSessionId() - Get current TUI-displayed session
• setForegroundSessionId(string) - Switch TUI to show specific session
• onLifecycle(callable) - Subscribe to lifecycle events (returns unsubscribe fn)

Other Changes

• Process flag: --server → --headless
• Added session.snapshot_rewind, session.shutdown, skill.invoked to SessionEventType enum
• Japanese docs: docs/jp/session-lifecycle.md

Usage

use Revolution\Copilot\Facades\Copilot;
use Revolution\Copilot\Types\SessionLifecycleEvent;

$client = Copilot::client();

// Subscribe to lifecycle events
$unsubscribe = $client->onLifecycle(function (SessionLifecycleEvent $event) {
    info("Session {$event->type->value}: {$event->sessionId}");
});

// Manage foreground session (TUI+server mode)
$sessionId = $client->getForegroundSessionId();
$client->setForegroundSessionId('session-123');

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