[AetherAI3]

Adds nano_qsearch, the q-search service that Predator Drive's NanoRuntimeQSearchBackend calls (V2 lane L3, gate G-W3). It takes the exact QSearchJobV1.to_payload() body on POST /qsearch/v1/submit and answers with a predator.qsearch.receipt.v1 that Predator's own QSearchReceiptV1.from_payload accepts. The wire contract is unchanged.

• Authenticated, replay-safe requests. X-Aether-Qsearch-Auth carries an HMAC-SHA256 over method, path, body hash, timestamp and nonce, with its own key file. The window is ±120 s and nonces are durable. Unauthenticated or replayed requests get a generic 401 and no receipt.
• Sealed receipts. Every receipt is HMAC-sealed over Predator-identical canonical JSON with a separate key. A golden vector produced by Predator's canonical_digest pins the encoding.
• Durable and idempotent. A SQLite store is keyed by job_digest, so an identical resubmit returns the stored receipt. After a crash, restart re-runs an accepted job once, with the same seed and the backend recorded at accept time. Hardware jobs are never run from recovery. The data directory is locked to one instance.
• Real engines, crash-isolated. ATLAS build_nucleus_program compiles ordinary and joint5 (via find_nuclei), transpiles to Heron {cz, rz, sx, x} on heavy-hex and keeps the smaller native 2Q count. Qiskit Aer then samples on statevector (n ≤ 20) or MPS, in a child process with OMP_NUM_THREADS=1, five tries and a per-job wall budget. A failure becomes NOT_RUN with a class-name reason. MPS reports the peak bond dimension from Aer's log. Every receipt here is classical simulation.
• IBM refuses by default. It needs AETHER_AQRC_HW_GO=1, an authority file, QPU seconds and a Fez target. Even then the ATLAS campaign_runtime delegate refuses, because no q-search purpose is qualified there yet.
• Packaging. The code lives in a top-level nano_qsearch/ package beside nano/, because tests/test_determinism_guards.py keeps clocks, environment, subprocesses and third-party imports out of nano/. The base install stays dependency-free. qiskit 2.3.1, qiskit-aer 0.17.2 and numpy come with the new aether-nano[quantum] extra, and the CLI is nano-qsearch-serve. Operator guide: docs/qsearch-service.md. Plan, evidence and hand-off notes: docs/superpowers/plans/2026-10-21-l3-qsearch-service.md.

Needs a Predator change (raised in the hand-off notes, not made here). Predator's default opener sends no auth header, so it gets NOT_RUN transport: HTTPError until Predator gains a signing opener and a request-key setting.

Tests. GitHub Actions is not running on private Aether repos right now, so these are local results. They were run from the repo root on Windows with system Python 3.12.10, qiskit 2.3.1, qiskit-aer 0.17.2, SQLite 3.49.1, ATLAS feat/qcompiler-find-nuclei and Predator-M origin/main 17ee3368:

$env:NANO_QSEARCH_ATLAS_PATH = "<aether-atlas checkout>"; $env:NANO_QSEARCH_PREDATOR_PATH = "<Predator-M checkout>"; $env:OMP_NUM_THREADS = "1"
python -m pytest -q -W ignore::DeprecationWarning --ignore=tests/test_provenance.py
1468 passed, 1 skipped

• tests/test_provenance.py has 7 failures that predate this branch: the installed aether_protocol_c rejects float fields. Neither that file nor nano/bridge is touched.
• In a plain venv with only pytest and pip install -e ., the suite gives 1370 passed, 4 skipped. The engine tests skip there.
• A live run of python -m nano_qsearch produced:
  • a signed pair02 POST that Predator accepted (statevector, joint5, agree true);
  • a resubmit that came back from the store in 0.11 s;
  • after killing the server mid-MPS-job and restarting it, recovered=1, a single re-run on the recorded backend, and attempts 2;
  • exit 2 for a second instance on the same data directory.

ATLAS counterpart: AetherAI3/AETHER-ATLAS#177.

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