fix: remove implicit narrowing conversion in CipherInputStream.skip

[sharmabikram]

Issue

GitHub code scanning flags an implicit narrowing conversion in CipherInputStream.skip(long) (alert code-scanning/3). The compound assignment currentPosition += n is int += long, which implicitly narrows the long back to int.

Fix

The buffered remainder (maxPosition - currentPosition) is bounded by the input buffer size (512 bytes by default) and always fits in an int. The requested skip is now clamped to that range as an int before the assignment, so:

• there is no implicit long -> int narrowing on the compound assignment, and
• the value added to currentPosition cannot overflow.

Behavior is unchanged for every input:

input	before	after
n within buffered remainder	skip n, advance	skip n, advance
n > buffered remainder	clamp to remainder	clamp to remainder
n == 0	return 0, no move	return 0, no move
n < 0	return 0, no move	return 0, no move
n > Integer.MAX_VALUE	clamp to remainder	clamp to remainder

Tests

Adds CipherInputStreamTest (5 cases, JUnit 5) covering skip within the buffer, clamping to the buffered remainder, zero, negative, and Long.MAX_VALUE inputs. mvn -Dtest=CipherInputStreamTest test -> Tests run: 5, Failures: 0, Errors: 0.

Notes

The pre-existing SME assessment on the internal tracking ticket is that this is a low-severity, benign finding (currentPosition never approaches Integer.MAX_VALUE in practice). This change resolves the static-analysis alert with a behavior-preserving refactor and adds test coverage where there previously was none for skip.

[sharmabikram]

Closing — will resubmit without a fork.