feat(test): cross-runtime test suite — PocketPaw, LangChain, CrewAI (#228)

[sshekhar563]

What

Adds tests/cross_runtime/ with 12 round-trip tests verifying .soul file portability across three AI frameworks.

Fixes #228

Tests

Runtime	Tests	Memory Types	Status
PocketPaw	6	Semantic + Episodic	✅ All passing
LangChain	3	Semantic	✅ All passing
CrewAI	3	Semantic	✅ All passing

What's Tested

• Semantic memory round-trip: Store → export → awaken → recall → verify content
• Episodic memory round-trip (PocketPaw): Same flow for event memories
• Identity preservation: name, DID survive export/import
• Memory count & importance scores: Metadata survives round-trip
• Double round-trip (PocketPaw): Re-export produces valid .soul
• Data serialization: model_dump() output compatible with LangChain/CrewAI stores

CI Safety

• Tests use pytest.importorskip() — skip when packages aren't installed
• Marked with @pytest.mark.cross_runtime for selective execution
• Zero risk to existing CI — no new dependencies required