Fix: log-system follow-ups for #703

[ChaoWao]

Summary

Three follow-up issues found post-merge of #703 (the V0..V9 log redesign).

1. pytest --log-level v0 was broken

pytest's CLI validator does:

int(getattr(logging, level.upper(), level))

so accepted level names must be module attributes on logging — logging.addLevelName alone is insufficient. addLevelName only registers _levelToName / _nameToLevel dicts, which pytest doesn't consult here.

Fix: also setattr(logging, "V0", 15) ... setattr(logging, "V9", 24) plus setattr(logging, "NUL", 60) and setattr(logging, "NULL", 60) (pytest upcases null → NULL before lookup). Done in two places:

• python/simpler/_log.py — for the standalone python test_*.py --log-level v3 path that goes through argparse after import simpler.
• conftest.py top-level — pytest validates the CLI value before conftest's first import simpler, so the module-level registration there is the one that actually saves pytest. The two registrations are redundant by design.

The addLevelName calls are kept for the side-benefit: %(levelname)s formatters now print V3 instead of Level 18.

2. L3/L4 chip subprocesses ignored the simpler logger

Worker.init() correctly snapshotted Python's simpler logger and forwarded it through ChipWorker.init(..., log_level, log_info_v) for the L2 path. The L3/L4 fork loops (_chip_process_loop and _chip_process_loop_with_bootstrap) called ChipWorker.init(...) without the new args, so each subprocess started its HostLogger / AICPU at the binding default (V5/INFO) regardless of what the user had configured.

Fix: added log_level / log_info_v parameters to both child loops (defaulted to 1, 5 for safety), and snapshot the parent's logger config once before the fork loop in _start_hierarchical — explicitly forwarded to each child invocation. After fork the child can't read the parent's logger state, so values must travel through the call site.

3. docs/testing.md was stale

The "Configuration sources" paragraph still described the C2-era model where Worker.run() snapshots into CallConfig.log_level per-task. Those CallConfig fields were dropped in C4; the snapshot is now one-shot at Worker.init(). Rewrote the paragraph and the Option Reference row to match the actual implementation, and documented the L3/L4 fork plumbing.

Test plan

• pytest --log-level v0/v3/v9/info/warn/error/null/debug all accepted (8 variants × 11 cases pass)
• cpput: 21/21
• py UT: 210/210 (excluding torch-only)
• Hardware st-onboard-* and CI to be exercised in PR CI

[gemini-code-assist]

Code Review

This pull request updates the logging infrastructure to support custom verbosity levels (V0-V9 and NUL) by registering them as attributes on the logging module for pytest compatibility. It also modifies worker initialization to snapshot and pass logging levels explicitly to forked child processes. Documentation was updated to describe these changes, and feedback was provided to clarify the technical requirements for pytest compatibility within the docs.