[Feature] Add tests for streaming angle encoder coverage

[viiccwen]

ref: #1058

What

Add focused tests for qdp/qdp-core/src/encoding/angle.rs.

Current coverage for this file is still zero:

• Function coverage: 0.00% (0/4)
• Line coverage: 0.00% (0/77)

Why

The streaming angle encoder has important validation branches that are not covered at all right now, including:

• qubit and sample-size mismatch
• chunk-size overflow checks
• non-finite angle rejection
• kernel launch path coverage

Without tests here, it is easy to break error messages or validation behavior without noticing.

How

Add tests under qdp/qdp-core/tests/ that exercise qdp/qdp-core/src/encoding/angle.rs, ideally through the same streaming entry point used in production.

Suggested coverage targets:

• reject sample_size == 0
• reject sample_size > STAGE_SIZE_ELEMENTS
• reject sample_size != num_qubits
• reject NaN and infinity with sample and angle index in the error
• add one happy-path encode that reaches the kernel launch path

This issue is done when encoding/angle.rs has meaningful non-zero coverage in cargo llvm-cov.

[yehfelareborn]

Take