[AI] Expand Test Coverage - eldritch-core/operations

[google-labs-jules]

This PR increases test coverage for the Eldritch DSL core operations.
Specifically, it adds:

• Unit tests for adjust_slice_indices in implants/lib/eldritchv2/eldritch-core/src/interpreter/operations/slicing.rs.
• Unit tests for apply_arithmetic_op in implants/lib/eldritchv2/eldritch-core/src/interpreter/operations/arithmetic.rs.

The tests cover:

• Standard arithmetic operations (+, -, *, /)
• Python-compatible floor division (//) and modulo (%) behavior
• Mixed Int/Float arithmetic
• Division by zero error handling
• Slice index normalization (negative indices, steps, bounds clamping)

These changes add critical coverage to core interpreter logic without modifying runtime behavior.

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PR created automatically by Jules for task 15393656514122785693 started by @KCarretto

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[github-actions]

Summary

Tests 📝	Passed ✅	Failed ❌	Skipped ⏭️	Other ❓	Flaky 🍂	Duration ⏱️
2995    ±0	2995    ±0	0    ±0	0    ±0	0    ±0	0    ±0	1ms    ±0

Previous Results

Build 🏗️	Result 🧪	Tests 📝	Passed ✅	Failed ❌	Skipped ⏭️	Other ❓	Flaky 🍂	Duration ⏱️
#430	✅	2995	2995	0	0	0	0	30.5s

Insights

Average Tests per Run	Total Flaky Tests	Total Failed	Slowest Test (p95)
2995	0	0	7.4s

Slowest Tests

Test 📝	Results 📊	Duration (avg) ⏱️	Duration (p95) ⏱️
eldritch: process::kill_impl::tests::test_process_kill	3	2.5s	7.4s
eldritch: process::kill_impl::tests::test_process_kill	3	2.5s	7.4s
eldritch: process::kill_impl::tests::test_process_kill	3	2.5s	7.4s
eldritch: random::string_impl::tests::test_string_length	3	5.7s	6.5s
eldritch: random::string_impl::tests::test_string_length	3	5.7s	6.5s
eldritch: random::string_impl::tests::test_string_length	3	5.7s	6.5s
eldritch: random::string_impl::tests::test_string_uniform	3	2.2s	6.5s
eldritch: random::string_impl::tests::test_string_uniform	3	2.2s	6.5s
eldritch: random::string_impl::tests::test_string_uniform	3	2.2s	6.5s
eldritch: regex::match_all_impl::tests::test_multi_match	3	2.2s	6.5s

_{🎉 No failed tests in this run. | 🍂 No flaky tests in this run.}

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