Misc CI hygiene bundle. Three independent changes:

1. Sanity check + streaming test fix

Pytest-style tests under test/registered/ have been silently skipping in CI: the CI runner invokes each file via python3 file.py -f (not pytest), so files without an executable if __name__ == "__main__": block just import and exit zero. Every test function body has never run.

• Sanity check in collect_tests: every registered file with at least one enabled registry must have an executable __main__ block (AST-verified). Files with all registries disabled=... (helpers, self-skipping multi-GPU benches) are exempt.
• Streaming session unit test fix (the immediate trigger): _FakeReq.finished_len = None (missing from fixture; real Req defaults to None) + proper __main__ entry. Also dropped a stale test (defers_tail_free) whose intent was already superseded by streaming session: trim spec v2 overshoot in cache_finished_req #22897.

Root cause (for context)

• run_unittest_files -> subprocess.Popen(["python3", <file>, "-f"]) — assumes unittest.main() picks up -f as --failfast.
• Pytest-style files with no unittest.main() / no __main__ block just import + exit 0. Zero tests executed, CI shows green.
• Easy to land silently during review, especially when migrating tests across directories.

Kept files (6): __main__ fix applied, tests now actually run

• test/registered/unit/mem_cache/test_streaming_session_unit.py — PR's immediate target (4 tests)
• test/registered/debug_utils/comparator/test_preset.py
• test/registered/debug_utils/source_patcher/test_code_patcher.py
• test/registered/debug_utils/source_patcher/test_dumper_integration.py
• test/registered/debug_utils/source_patcher/test_source_editor.py
• test/registered/debug_utils/test_dump_comparator.py — also dropped TestMainBasic subset: those 3 integration tests call dump_comparator.main() which hard-codes x.cuda() in _load_tensor, so they always raise no NVIDIA driver on the CPU suite they were registered in. Kept the 6 pure-CPU unit tests in the file. cc @fzyzcjy (originally added in Tiny fix single-gpu dumper and add tests for dumper #16285)

Dropped files (9)

• test/registered/quant/test_bnb.py — cc @yhyang201
• test/registered/quant/test_int4fp8_moe.py — cc @fxmarty-amd (content [AMD][Quantization] Add int4fp8_moe online quantization on ROCm #7392), @Ying1123 (framework Add accuracy test to CI: MMLU #882)
• test/registered/amd/test_zimage_turbo.py — cc @michaelzhang-ai
• python/sglang/jit_kernel/tests/test_dependency.py — cc @DarkSharpness
• test/registered/ops/test_repeat_interleave.py — cc @yuan-luo
• test/registered/unit/function_call/test_glm47_moe_detector.py — cc @Leoyzen
• test/registered/unit/model_executor/test_model_hooks.py — cc @Carlomus
• test/registered/rotary/test_mrope.py — cc @yuan-luo (initial), @raayandhar (yarn feat feat: Support mrope_section with rope_type: "yarn" #13313)
• test/registered/vlm/test_patch_embed_perf.py — perf assertion (linear-vs-conv3d speedup), prone to flakiness on shared GPU runners; silent-skip since day one. cc @yuan-luo

If any original author wants a file revived: reopen with a proper __main__ block (see the pattern in test_streaming_session_unit.py at the bottom) so the file actually executes in CI.

2. Fix rerun-test.yml CPU job missing protoc / rustup

rerun-test-cpu (.github/workflows/rerun-test.yml) was runs-on: ubuntu-latest but missing the Install protoc + Install Rust toolchain steps that pr-test.yml's stage-a-test-cpu has (at pr-test.yml:646-652). Installing sglang editable wheel compiles sglang-grpc Rust crate, whose build.rs needs protoc -> workflow fails in Install dependencies before pytest even starts.

Fix: mirror pr-test.yml's setup — add the same two steps. Keeps rerun-test environment aligned with pr-test rather than forking into a docker-container approach.

Test plan

• collect_tests(sanity_check=True) passes over all 710 registered files
• scripts/ci/check_registered_tests.py returns 0 (pre-commit hook stays green)
• Each previously-silent file: syntax-check + pytest AST-parse OK
• CI green on the 6 kept files (dispatched via /rerun-test)