feat: health check suite — CPU, memory, interface errors, log alerts

[Copilot]

Adds composable, vendor-aware health checks (CPU, memory, interface error counters, log scanning) with JSON output for monitoring integration, runnable against a single host or an inventory group.

Bug fix

• netops/parsers/nokia_sros.py: __all__ was placed between the function signature and its docstring, causing an IndentationError that broke the entire parsers module and all dependent tests.

New: netops/parsers/health.py

Pure-text parsers for health telemetry across two vendor families:

Parser	Command	Vendor
parse_cpu_cisco / parse_cpu_nokia	show processes cpu / show system cpu	Cisco / Nokia
parse_memory_cisco / parse_memory_nokia	show processes memory / show system memory-pools	Cisco / Nokia
parse_interface_errors_cisco / parse_interface_errors_nokia	show interfaces / show port detail	Cisco / Nokia
parse_logs_cisco / parse_logs_nokia	show logging / show log 99	Cisco (sev 0–3) / Nokia (CRITICAL/MAJOR)

New: netops/check/health.py

Composable check functions wired into run_health_check(), which returns a structured result with per-check alert: bool and a rolled-up overall_alert. Supports both single-host and inventory-based execution.

# Inventory group with custom thresholds
python -m netops.check.health --inventory inv.yaml --group core --threshold cpu=80,mem=85

# JSON output for monitoring integration
python -m netops.check.health --host 10.0.0.1 --vendor cisco_ios --json

# Exit 1 on any alert (CI/alerting pipelines)
python -m netops.check.health --inventory inv.yaml --fail-on-alert

New: tests/test_health.py

105 unit tests covering all parsers, check helpers (via _MockConn), threshold parsing, and run_health_check() with monkeypatched DeviceConnection.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>feat: health check suite — CPU, memory, interface errors, log alerts</issue_title>
<issue_description>Composable health checks that work across vendors.

• CPU utilization check with threshold alerting
• Memory utilization check
• Interface error counter check (CRC, input/output errors, drops)
• Log scanning for critical/major events
• JSON output for monitoring integration

python -m netops.check.health --inventory inv.yaml --group core --threshold cpu=80,mem=85
```</issue_description>

## Comments on the Issue (you are @copilot in this section)

<comments>
</comments>

• Fixes feat: health check suite — CPU, memory, interface errors, log alerts #4

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