OPENNLP-1836: Fix input encoding in SentenceVectorsDL

[krickert]

See https://issues.apache.org/jira/browse/OPENNLP-1836

SentenceVectorsDL sent an all-zero attention_mask and all-one token_type_ids to the ONNX model, so the encoder attended to nothing. This fixes the encoding to the standard single-segment BERT convention (mask=1, types=0), consistent with DocumentCategorizerDL, and additionally:

• closes the OnnxTensor inputs and OrtSession.Result (native memory leak)
• replaces the NPE on a vocabulary miss with a descriptive IllegalArgumentException
• adds a unit test for the encoding (tokenize is now package-private static, no ONNX session needed)
• updates SentenceVectorsDLEval expectations

Eval values were verified empirically: the unfixed code reproduces the previously pinned values exactly against the public sentence-transformers/all-MiniLM-L6-v2 ONNX export, and the corrected encoding produces the new pinned values (dimension 384).

Note: this is a behavioral fix - vectors persisted from the old encoding are not comparable with the corrected output and should be re-embedded.

[Copilot]

Pull request overview

Fixes SentenceVectorsDL’s ONNX input encoding so sentence-transformer models receive standard single-segment BERT inputs (attention mask = 1 for real tokens, token type ids = 0), aligning behavior with other DL components and updating expected eval outputs accordingly.

Changes:

• Corrects SentenceVectorsDL token encoding (mask/types) and improves vocabulary-miss handling with a descriptive exception.
• Prevents native-memory leaks by closing ONNX tensors and OrtSession.Result.
• Adds unit tests for tokenization/encoding and updates SentenceVectorsDLEval pinned vector expectations.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
opennlp-eval-tests/src/test/java/opennlp/dl/vectors/SentenceVectorsDLEval.java	Updates pinned expected vector values for the corrected encoding.
opennlp-core/opennlp-ml/opennlp-dl/src/test/java/opennlp/dl/vectors/SentenceVectorsDLTest.java	Adds unit tests validating single-segment BERT encoding and vocabulary/UNK behavior.
opennlp-core/opennlp-ml/opennlp-dl/src/main/java/opennlp/dl/vectors/SentenceVectorsDL.java	Fixes mask/types encoding, closes ONNX resources, and improves vocab-mismatch error reporting.

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[krickert]

Ran copilot against this. It didn't do a bad job because it only said that the expected vs actual were reversed.