🧪 Add tests for autoformalization_route_note_path in formalization.py

[Wenbobobo]

🎯 What: Adding a new test file tests/test_formalization.py to cover the autoformalization_route_note_path function and its internal string formatting helper _route_note_slug.
📊 Coverage: Tests handle the standard expected happy path along with various edge cases: files lacking a Lean extension, files with unsafe symbols, and empty file scenarios resulting in a fallback "objective" path.
✨ Result: Improved module test coverage. Changes were also locally verified to correctly catch deliberately injected failures.

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PR created automatically by Jules for task 11522391504796597566 started by @Wenbobobo

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[Copilot]

Pull request overview

Adds a focused pytest suite for archonlib.formalization path/slug generation used by autoformalization route notes, improving coverage around filename normalization and edge-case handling.

Changes:

• Introduces tests/test_formalization.py to validate _route_note_slug sanitization rules (Lean suffix stripping, slash-to-hyphen mapping, invalid character handling, and "objective" fallback).
• Adds assertions for autoformalization_route_note_path() to ensure it constructs the expected .archon/informal/<slug>-autoformalize.md path, including empty input behavior.

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