CES-70 — import spec + CES-71 cadence-units audit (docs only)

[JMNofziger]

Spec / discovery pass for CES-70. No application code, no schema migration, no CES-71 rename.

What

• docs/specs/export-import.md — normative import spec, audited from the shipped CES-41 assembler (PR #21) rather than the 2026-04 body of export-v1.md.
• docs/product/prompts/ces-70-import.md — execution prompt, held at BLOCKED.
• docs/specs/README.md — index row.

Cadence audit (blocking) — CLEAN

maintenance_rules.cadence_km stores canonical meters on every write path, so CES-71 stays a cosmetic rename.

• upsertReminderRule is the only writer; it passes cadenceKmMeters through unconverted.
• maintenance_page._save is the only caller and converts via distanceToMeters(value, prefs); _loadRule round-trips via metersToDisplayWhole.
• Raw SQL in constraints_test.dart / roundtrip_test.dart writes NULL cadence to exercise the table CHECK — no unit exposure.
• Repo-test values 10_000_000 / 15_000_000 are 10 000 / 15 000 km — intent matches meters.
• No cadence references in PWA-lite or tests/client-db/fixtures/.

Runtime confirmation:

km entry 10   -> 10000 m stored        10000 m    -> 10 km shown
km entry 5000 -> 5000000 m stored      16093 m    -> 10 mi shown
mi entry 10   -> 16093 m stored        10000000 m -> 10000 km shown
mi entry 5000 -> 8046720 m stored

One real gap, not a bug: the form-level conversion at maintenance_page._save is untested. maintenance_page_test.dart fills only the months field; the repository test passes meters directly, bypassing distanceToMeters. CES-71 renames exactly that path and should add the assertion.

Locked in the spec

Canonical INT64 only (derived columns must be present but are never read) · strict A1 headers imported from client/lib/export/headers.dart so export and import cannot drift · cadence_km verbatim meters · photos fail closed via the CES-40 guard · imported rows stay never-synced (row_version NULL, no outbox enqueue) · ids preserved, never remapped · single-transaction atomicity · FK-parent apply order with orphan rejection · identity advisory only, settings.id never overwritten · foreground-only UX.

Plus a 15-code error table and a 15-item test list.

Deliberately NOT decided

Merge vs replace is a product lock (CES-70 says so). The spec gives both options, a recommendation — replace, behind a typed confirmation, because a merge can never express deletions and LWW merge pre-empts the v1.x rules ADR 002 deferred — and the cost of guessing wrong in either direction. Decision 0 in the prompt is the one line that unblocks implementation.

Also flagged for product: cross-account imports are permitted by design (hash mismatch is a warning, not a rejection) — confirm or override.

Verification

flutter analyze clean · python3 ci/telemetry-gate.py PASS · 247 client tests green · change set is docs-only (tracked and filesystem Dart counts both 90, unchanged).

One forward-reference link in the prompt points at client/lib/export/, which resolves when PR #21 merges — the prompt already lists that merge as a prerequisite.