fix: Generate personless IDs with UUID v7

[marandaneto]

💡 Motivation and Context

Generated personless identifiers should be time-ordered UUID v7 values. The PHP SDK still generated v4 values for personless capture distinct IDs and exception auto-capture fallback IDs.

This PR adds internal UUID v7 generation following the RFC 9562 Unix timestamp layout and uses it for SDK-generated personless distinct_id values. The helper is autoloaded internally without adding Uuid::v7() to the public API snapshot.

💚 How did you test it?

• composer validate
• composer api:check
• vendor/bin/phpcs --warning-severity=0 lib/Uuid.php lib/Client.php lib/ExceptionCapture.php test/UuidTest.php
• vendor/bin/phpunit --no-coverage test/UuidTest.php
• vendor/bin/phpunit --no-coverage test/RequestContextTest.php --filter Personless
• vendor/bin/phpunit --no-coverage test/ExceptionPayloadBuilderTest.php --filter testCaptureExceptionWithoutDistinctIdGeneratesUuidAndSetsNoProfile
• vendor/bin/phpunit --no-coverage test/ExceptionCaptureTest.php --filter testExceptionHandlerUsesCurrentClientContextProperties

📝 Checklist

• I reviewed the submitted code.
• I added tests to verify the changes.
• I updated the docs if needed.
• No breaking change or entry added to the changelog.

If releasing new changes

• Ran pnpm changeset to generate a changeset file

🤖 Agent context

Autonomy: Human-driven (agent-assisted)

Implemented by a coding agent from a human request to migrate SDK-generated UUID v4/random IDs to UUID v7. Follow-up review feedback made UUID v7 generation internal rather than public API and documented the RFC 9562 layout / no PHP core UUID v7 API in supported runtimes.

[greptile-apps]

_{Reviews (1): Last reviewed commit: "fix: generate personless ids with UUID v..." | Re-trigger Greptile}