Refactor: Split cortex/engine/causality.py

[borjamoskv]

Split cortex/engine/causality.py into a new cortex/engine/causality_graphs package containing sync_graph.py and async_graph.py. Kept original causality.py as a clean wrapper to re-export the exact same API. This satisfies the project's Ω₂ Entropic Asymmetry axiom requiring modules to be <= 500 lines of code.

All relevant tests still pass, meaning no functional changes were made. No new bugs introduced. Code was reviewed, and tests for both regression and function were run natively on the machine via pytest.

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PR created automatically by Jules for task 18438197279569264773 started by @borjamoskv

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[github-actions]

∞ MÖBIUS — PR Analysis

Metric	Value
Files changed	4
Total changes	934 (+/-)
Complexity	critical
Est. review time	60 min
Has tests?	⚠️ Missing
Has Rust changes?	No

Labels applied: engine

Warning

No test files detected in this PR. Consider adding tests.

Caution

This PR has >500 lines of changes. Consider splitting into smaller PRs.

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