Parameterize the closed-stream "operation after close throws" tests

[dfa1]

Background

ZstdStreamTest has four near-identical tests that each set up a stream, close it, then assert an operation throws:

• writeAfterCloseThrows() (~L294)
• flushAfterCloseThrows() (~L309)
• readAfterCloseThrows() (~L361)

They differ only in which method is called after close(). That's copy-paste that a single @ParameterizedTest expresses better.

Task

Collapse the "operation after close throws" cases into one @ParameterizedTest driven by a @MethodSource of (name, ThrowingCallable) pairs (or similar). Keep each scenario's intent visible via the source's display name.

Acceptance criteria

• One parameterized test replaces the per-operation copies; behavior unchanged.
• Follows the repo test conventions in CLAUDE.md: // Given / // When / // Then, exception asserted via assertThatThrownBy(result) where result is the ThrowingCallable captured under // When.
• ./mvnw -pl zstd test stays green.

Pointers

• zstd/src/test/java/io/github/dfa1/zstd/ZstdStreamTest.java