Validate deque capacity before allocation

[krotname]

Motivation

• Fix an availability vulnerability where the deque capacity read from stdin was used directly in new int[cap], allowing NegativeArraySizeException for negative input and OutOfMemoryError for very large input.
• Ensure the CLI kata does not crash or destabilize a shared judge process when given malformed or adversarial stdin.

Description

• Introduce a MAX_CAPACITY bound (100_000) and a safeCapacity(int) helper to normalize capacities before allocation in src/main/java/algorithms/sprint2/Deque.java.
• Replace the direct allocation new int[cap] with new int[this.cap] where this.cap is the sanitized value returned by safeCapacity.
• Treat negative capacities as 0 and cap excessively large capacities to MAX_CAPACITY to avoid allocating uncontrolled memory.
• Add in-file regression checks exercising negative and very large input cases so malformed stdin produces controlled error outputs instead of crashing.

Testing

• Compiled the class with javac -d /tmp/deque-classes src/main/java/algorithms/sprint2/Deque.java and the compilation succeeded.
• Ran the built tests with java -Dos.name=Windows -cp /tmp/deque-classes algorithms.sprint2.Deque which printed Test OK, indicating existing tests pass.
• Reproduced malformed inputs by piping 1\n-1\npop_front\n and 0\n1000000000\n to the program (the latter with -Xmx32m) and observed controlled error outputs without NegativeArraySizeException or OutOfMemoryError, confirming the fix.

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[sonarqubecloud]

Quality Gate passed

Issues
3 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[krotname]

Закрываю как superseded by #116: изменения перенесены в одну проверенную ветку, все review findings учтены; локальный mvn verify прошёл полностью.