refactor: split rank-E report and snapshot helpers

[axisrow]

Part of #1131

Summary

• Split src/runtime/worker.py::_publish_snapshots into private snapshot/payload helpers while preserving snapshot publish order and the chore(worker): не спамить полным трейсбэком при таймауте снапшота нотификейшн-бота #1172 asyncio.TimeoutError notification-bot branch.
• Split ChannelAnalyzer._build_report into fetch/build/flag/report helper methods while preserving flag ordering and report construction.
• Added scripts/verify_refactor_ast_equivalence.py to compare the extracted helper composition against origin/main AST blocks.

Code health delta

Before python scripts/code_health.py --top 40:

• CC distribution: A:3483 B:502 C:221 D:34 E:8 F:0, average 3.46.
• Targets: _publish_snapshots E(40), ChannelAnalyzer._build_report E(32).

After python scripts/code_health.py --top 40:

• CC distribution: A:3506 B:507 C:221 D:34 E:6 F:0, average 3.44.
• Target ranks from radon cc -s src/runtime/worker.py src/filters/analyzer.py: _publish_snapshots A(1), ChannelAnalyzer._build_report A(2).

AST proof

• python scripts/verify_refactor_ast_equivalence.py --base-ref origin/main passed.
• The script checks helper call order and extracted AST blocks for worker setup, snapshots, queue payload, notification payload/snapshot type, analyzer map fetch, per-flag logic, result constructor, and final report.

Validation

• ruff check src/ tests/ conftest.py passed.
• pytest tests/test_runtime_worker.py -v passed: 19 passed.
• pytest tests/test_filters.py -v passed: 53 passed.
• pytest tests/test_db_access_conventions.py tests/test_test_levels.py -q passed: 17 passed.
• pytest tests/ -v -m aiosqlite_serial passed: 943 passed, 9266 deselected.
• pytest tests/ -v -m "not aiosqlite_serial" -n auto completed but failed outside this refactor scope: 7 failures in tests/test_quality_scoring_service.py, tests/routes/test_debug_routes.py::test_debug_memory_returns_json, and tests/test_pipelines.py::test_pipelines_page_renders.

[axisrow]

Дубликат партии 1 #1131 — та же работа (split _publish_snapshots + _build_report) уже смержена через #1197 (commit 7a9ef80). Этот PR открыл воркер -7 перед зависанием; работа была забрана оркестратором, провалидирована (AST-эквивалентность + 72 теста + dual-review Claude+Codex APPROVE) и смержена как #1197 без одноразового AST-скрипта (он засорял ruff). Закрываю как superseded.