[DO NOT MERGE] test(memory-monitor): aggressive thresholds + tighter intervals for fleet testing

[devin-ai-integration]

Summary

🚨 DO NOT MERGE — this branch exists only to stress-test fail-fast behavior on real connectors by lowering thresholds and tightening check intervals so the monitor trips on workloads that would normally stay well under the production gates. It is stacked on top of #995 (devin/1776796633-lower-memory-thresholds) for direct comparison.

Aggressive test-only values in airbyte_cdk/utils/memory_monitor.py:

Knob	main	#995 (production-track)	This branch (test)
_CRITICAL_THRESHOLD	0.98	0.95	0.80
_ANON_SHARE_OF_USAGE_THRESHOLD	0.85	0.85	0.75
_HIGH_PRESSURE_THRESHOLD	0.95	0.90	0.50
_DEFAULT_CHECK_INTERVAL	5000	5000	100
_HIGH_PRESSURE_CHECK_INTERVAL	100	100	5

Tests updated to match the aggressive values (36 unit tests in unit_tests/utils/test_memory_monitor.py pass locally; ruff / format / mypy clean).

Notes

• Branches off devin/1776796633-lower-memory-thresholds, so the diff is only the aggressive delta. The humanized byte formatting, startup config log, and docstring cleanups from fix(memory-monitor): lower fail-fast thresholds and humanize diagnostic messages #995 are inherited.
• Intended usage: build a CDK prerelease from this branch and pin it on a high-memory actor (or the test connectors the team is using to reproduce the silent-OOM class) to observe:
  • Whether the trace now surfaces on workloads that previously silent-failed.
  • False-positive rate — how often the tighter anon-share gate (75%) raises on workloads that are healthy.
  • Overhead of check_interval=100 (and 5 once high pressure latches).
• The top of the constants block carries an inline # WARNING: DO NOT MERGE banner so a stray merge attempt is obvious in review.

Review & Testing Checklist for Human

• Confirm this PR stays in draft and is never merged to main.
• After testing, either (a) pull validated numbers into fix(memory-monitor): lower fail-fast thresholds and humanize diagnostic messages #995 and close this, or (b) close this unchanged.
• If you want different aggressive values, tell Devin — all five knobs are isolated to memory_monitor.py:_CRITICAL_THRESHOLD / _ANON_SHARE_OF_USAGE_THRESHOLD / _HIGH_PRESSURE_THRESHOLD / _DEFAULT_CHECK_INTERVAL / _HIGH_PRESSURE_CHECK_INTERVAL.

Link to Devin session: https://app.devin.ai/sessions/45e85918168d472d9e4e6e134a134fbc

[devin-ai-integration]

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[github-actions]

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/prerelease

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[github-actions]

PyTest Results (Fast)

4 034 tests  ±0   4 023 ✅ ±0   7m 44s ⏱️ -5s
    1 suites ±0      11 💤 ±0 
    1 files   ±0       0 ❌ ±0 

Results for commit fed5c22. ± Comparison against base commit 5a054f8.

[github-actions]

PyTest Results (Full)

4 037 tests  ±0   4 025 ✅ ±0   11m 17s ⏱️ -7s
    1 suites ±0      12 💤 ±0 
    1 files   ±0       0 ❌ ±0 

Results for commit fed5c22. ± Comparison against base commit 5a054f8.