Record every UK build attempt in Logbook

[juaristi22]

Part of workstream A of the UK-migration master epic (#665). Should land before the P1 calibration work starts generating intermediate builds — Logbook is the migration's build-attempt memory.

#628 delivered the append-only Logbook: hash-chained rows (pipeline, rung, seed, code_pin, input_pins_digest, identity_digest, phases_reached, gate_verdicts, wall_seconds, cost_usd, artifact_location, disposition), durable local spool first, best-effort Supabase insert (remote availability never part of build correctness). But adoption is per-tool, and today only tools/build_us_multispine_pool.py calls the record_build_attempt seam — no UK driver or uk_runtime module references Logbook at all.

Scope

• Wire record_build_attempt into the three UK drivers: tools/build_uk_national_dataset.py (all rungs of the UK builds inherit the scale ladder from day one (sample_fraction in the #612 Frame carrier) #627 ladder, including sampled rungs and rung_abort exits), tools/build_uk_rowwise_dataset.py, and tools/build_uk_rowwise_candidate.py. Failed attempts and refused release candidates record a row with the appropriate disposition — the point is that discarded intermediate builds remain visible.
• Populate gate_verdicts from the schema-4 battery report and artifact_location from the staging/candidate output path; input_pins_digest covers the certified-spine sha and (once Consume Ledger UK facts: uk_target_references, mapping module, and a compile-parity gate #622/Calibrate the UK national build from Ledger-backed targets #623 land) the ledger_facts_sha256.
• Chain coordination per the module contract (caller supplies prev_row_digest; spool write is fatal on failure, remote insert is not).
• Fix in passing: the microcosm/build/logbook.py docstring points adoption ownership at The stacked spine: one origin-labeled spine, banked gap-fill, null-vs-zero doctrine, by-origin battery (#578 revision pilot) #616, which is the merged stacked-spine PR — repoint it at this issue / UK dataset build: full migration from policyengine-uk-data (master epic) #665.

Out of scope

• The exact-k publication/discovery surface (Epic: publish and discover exact-k dataset families through Logbook and immutable Hugging Face releases #637, Logbook: record requested and realized exact-k cardinality #641) — the UK exact-k lane (workstream H of UK dataset build: full migration from policyengine-uk-data (master epic) #665) inherits that epic once it exists.
• POPULACE_LEDGER_* → POPULACE_LOGBOOK_* env renames (Rename POPULACE_LEDGER_* client env vars to POPULACE_LOGBOOK_* #640).

Acceptance

Running any UK driver at any rung — pass, fail, or abort — appends exactly one validated row to the spool/archive, and tools/logbook.py render shows the UK attempt chain alongside the US one.