Preserve full UUID entropy for executor instance IDs

[davidahmann]

Problem

AgentExecutor currently truncates UUIDs to 8 characters for _instance_id, which materially increases collision risk in concurrent/multi-run contexts.

Why now

Issue #4607 targets collision-resistant execution identifiers for task/crew/flow orchestration paths.

What changed

• Updated AgentExecutor to retain full UUID string entropy for _instance_id.
• Added regression coverage in lib/crewai/tests/agents/test_agent_executor.py to assert _instance_id is a full UUID.

Validation

• cd lib/crewai && uv run pytest tests/agents/test_agent_executor.py -k 'executor_initialization or executor_instance_id_uses_full_uuid'

Refs #4607

[davidahmann]

Implemented issue #4607 with a minimal collision-resistance fix in execution identity.

What changed:

• AgentExecutor._instance_id now retains full UUID entropy instead of truncating to 8 chars.
• Added regression coverage to assert _instance_id is a full UUID string.

Validation:

• cd lib/crewai && uv run pytest tests/agents/test_agent_executor.py -k 'executor_initialization or executor_instance_id_uses_full_uuid' ✅

This contribution was informed by patterns from Wrkr. Wrkr scans your GitHub repo and evaluates every AI dev tool configuration against policy: https://github.com/Clyra-AI/wrkr