Move all tests from src/tests to tests/ folder and ensure 100% tests coverage

[konard]

Summary

• Moved all tests from ./src/tests/ to ./tests/ folder, converting them from unit tests to integration tests
• Shared test fixtures (TestAbsoluteList, TestRelativeList, TestTree) placed in tests/common/mod.rs
• Added 10 new tests to improve coverage of edge cases and code paths
• Total: 115 tests (42 list + 67 tree + 6 public API compatibility)
• All unsafe code is encapsulated in test fixtures and thoroughly exercised

Changes

File	Action
src/tests/mod.rs	Moved → tests/common/mod.rs (shared test fixtures)
src/tests/list_tests.rs	Moved → tests/list_tests.rs
src/tests/tree_tests.rs	Moved → tests/tree_tests.rs
src/lib.rs	Removed #[cfg(test)] mod tests;

New tests added for coverage

• test_detach_node_with_right_child_only — covers *root = *right path in detach_core
• test_attach_right_special_case_empty — covers right-side special case in attach_core
• test_detach_replacement_from_right_subtree — covers replacement from right subtree path
• test_get_rightest_single_node / test_get_leftest_single_node — covers single-node edge cases
• test_get_left_size_no_left_child / test_get_right_size_no_right_child — covers zero-child paths
• test_fix_size_leaf_node — covers fix_size with no children
• test_detach_reinsert_cycle — covers full detach-all and reinsert cycle
• test_contains_deep_tree — covers deep tree traversal in contains

Coverage analysis

All code paths in the library are exercised:

• LinkType: funty() method with all unsigned types and full u8 range
• LinkedList: All 4 abstract methods through implementations
• AbsoluteLinkedList: All methods including inc_size/dec_size
• AbsoluteCircularLinkedList: All 5 methods with all branch paths (empty/non-empty, first/last/middle)
• RelativeLinkedList: All methods including multiple heads
• RelativeCircularLinkedList: All 5 methods with all branch paths
• RecursiveSizeBalancedTree: All 20+ methods including rotations, traversal, and edge cases
• IterativeSizeBalancedTree: attach/detach with all rotation paths, special cases, and replacement strategies

Fixes #24

🤖 Generated with Claude Code

[konard]

🤖 Solution Draft Log

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💰 Cost estimation:

• Public pricing estimate: $9.770764
• Calculated by Anthropic: $5.542879 USD
• Difference: $-4.227885 (-43.27%)

📊 Token budget statistics:

• Context window: 12,380,979 / 1,000,000 tokens (1238.10%)
• Output tokens: 40,898 / 128,000 tokens (31.95%)
• Own calculation (stream): 494,212 tokens (172 events)
• JSONL calculation: 485,774 tokens (diff: -1.71%)

🤖 Models used:

• Tool: Anthropic Claude Code
• Requested: opus
• Main model: Claude Opus 4.6 (claude-opus-4-6)
• Additional models:
  • Claude Haiku 4.5 (claude-haiku-4-5-20251001)

📎 Log file uploaded as Gist (1929KB)

• View complete solution draft log

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[konard]

✅ Ready to merge

This pull request is now ready to be merged:

• All CI checks have passed
• No merge conflicts
• No pending changes

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