This PR targets the following PR:

• feat(cdk): enable fail-fast shutdown on memory threshold with dual-condition check #962

Summary

Adds a synthetic cache memory pressure scenario in AirbyteEntrypoint.read() to test the negative case of the dual-condition memory monitor (introduced in #962). For each consumed record, a 10 MB file-backed mmap page is created on /tmp (overlay fs), which inflates cgroup memory usage without increasing the Python process's anonymous RSS (RssAnon).

This validates that the memory monitor correctly does not raise AirbyteTracedException when container memory is high but the pressure comes from file-backed/reclaimable pages rather than process-private anonymous memory.

DO NOT MERGE — test-only change to validate memory monitor behavior.

Companion PR: #969 (tests the positive case — process RSS growth triggers fail-fast)

Updates since last revision

• Switched mmap backing store from /dev/shm (tmpfs) to /tmp (overlay fs) to fix SIGBUS (exit code 135). Docker containers typically cap /dev/shm at 64 MB, so after ~6 records the tmpfs filled up and the next mm.write() triggered a bus error before the memory monitor ever got a chance to evaluate. /tmp on overlay fs has no such hard limit, and file-backed mmap pages there still count toward cgroup memory as RssFile (not RssAnon), preserving the dual-condition test.

Review & Testing Checklist for Human

• Verify that mmap pages backed by /tmp (overlay fs) actually inflate cgroup memory.current in the target deployment environment — overlay fs page cache accounting can vary by kernel version and storage driver
• Deploy a connector using this branch in a memory-bounded container and confirm cgroup usage climbs toward the limit
• Confirm that RssAnon in /proc/self/status remains low relative to the container limit
• Verify the memory monitor logs the "pressure likely from file-backed or reclaimable pages — not raising" info message instead of raising an exception
• Confirm the sync completes (or is killed by the OOM killer) without a graceful AirbyteTracedException shutdown

Notes

• The mmap pages and file descriptors are intentionally never closed — the goal is to accumulate memory pressure throughout the sync
• Uses tempfile.mktemp (which has a theoretical race condition) rather than tempfile.mkstemp; acceptable for a throwaway test branch
• Each record creates a 10 MB mmap'd file on /tmp; memory growth rate depends on record throughput
• If overlay fs pages are too aggressively reclaimed by the kernel and cgroup usage never reaches the 98% critical threshold, the test may not exercise the dual-condition code path — check the memory monitor warning logs to confirm cgroup usage is actually climbing
• Pattern is the counterpart to DO NOT MERGE: test graceful OOM shutdown via intentional memory leak #969, which tests that process-private memory growth does trigger fail-fast

Link to Devin session: https://app.devin.ai/sessions/070ecb51ceee4f9189e1c09a83ba31cb