chore(tests): disk_v2 antithesis test harness + exercisers

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Summary

The Antithesis test harness for disk buffer v2: two self-driving exercisers
(disk_v2_antithesis — the #21683 accounting cluster; disk_v2_lossfinder — a
7-scenario data-loss fault menu with a no-silent-loss oracle), plus Dockerfiles,
docker-compose configs (block / drop variants / direct / lossfinder), the Vector-
SUT workload, and the test templates under tests/antithesis/test/v1. Registers
the two examples + a serde_json dev-dep.

Stack (Antithesis-driven disk buffer v2 data-loss investigation):

• docs(buffers): disk_v2 data-loss research scratchbook #25524 — research scratchbook (docs)
• chore(unit tests): failing disk_v2 bug demonstrations #25525 — failing bug-demonstration tests
• feat(buffers): SUT-side antithesis underflow assertions #25526 — SUT-side assertions
• chore(tests): disk_v2 antithesis test harness + exercisers #25527 — test harness + exercisers

How did you test this PR?

cargo build -p vector-buffers --example disk_v2_antithesis --example disk_v2_lossfinder;
snouty validate on both config dirs (reaches setup_complete, test commands
discovered); local smoke runs of both exercisers. Antithesis runs reproduced #21683
and the finalizer status-discard loss.

Change Type

• Bug fix
• New feature — test infrastructure (no runtime behavior change)
• Dependencies
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

Does this PR include user facing changes?

• Yes.
• No. A maintainer will apply the no-changelog label to this PR.

References

• Related: buffer_byte_size has value 18446744073709548000 #21683, vector_component_discarded_events_total metric not showing/incrementing for gcp_pubsub sink when disk buffer is full (drop_newest) #24606, Sinks configured with disk buffers cause partial stall of pipeline on config reload #24948

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Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• chore(tests): disk_v2 antithesis test harness + exercisers #25527 👈 (View in Graphite)
• feat(buffers): SUT-side antithesis underflow assertions #25526
• chore(unit tests): failing disk_v2 bug demonstrations #25525
• docs(buffers): disk_v2 data-loss research scratchbook #25524
• master

This stack of pull requests is managed by Graphite. Learn more about stacking.

[datadog-vectordotdev]

✨ Fix all issues with Cursor

⚠️ Warnings

🧪 7 Tests failed

buffer_usage_data::tests::drop_newest_drops_should_increment_component_discarded_metric_issue_24606 from vector-buffers     (Fix with Cursor)

Test has failed

variants::disk_v2::tests::acknowledgements::rejected_delivery_should_not_advance_acks_finalizer_status_discard from vector-buffers     (Fix with Cursor)

Test has failed

variants::disk_v2::tests::invariants::delete_completed_data_file_size_delta_should_saturate_reader_524 from vector-buffers     (Fix with Cursor)

Test has failed

View all

ℹ️ Info

No other issues found (see more)

❄️ No new flaky tests detected

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