docs(plans): implementation plan — wave-based decomposition; wave 1 decomposed into tasks/

- docs/plans/implementation.md: the meta plan (alkstore pattern) — nine
  waves, dependency logic, decided points, review gates. Scope authority:
  v0.1.0 ships the full surface (all five engines, fleet GC, ops).
- Wave 1 decomposed: scaffold-crate-features, core-error-model,
  core-hashing-keys, core-trait-and-types, suite-scaffold,
  review-wave-1 (the one-way-door gate).
- Waves 2-9 shaped in the plan; each decomposes after the prior wave's
  review gate.

Verification: cargo test / clippy -D warnings / fmt --check green
(docs-only change).

tasks/suite-scaffold.md

@@ -0,0 +1,73 @@
+---
+id: suite-scaffold
+name: Conformance suite — home, convention, and invariant backlog
+status: pending
+depends_on: [scaffold-crate-features]
+scope: narrow
+risk: low
+impact: project
+level: implementation
+tags: [wave-1, suite]
+---
+
+## Description
+
+Establish `tests/conformance/` — the in-crate conformance harness home
+(decided point: engines are features of one crate, so the suite lives
+in-crate, factory-parameterized over engine constructors; the
+alkstore ADR-017/022 pattern adapted) — with the convention that waves
+2–6 grow columns against:
+
+- **The convention document** (a `tests/conformance/README.md` or
+  module doc): row naming, the ADR-stamp format (every row cites the
+  ADR § / spec § that pins it — the alkstore version-stamping
+  convention), the one-normative-owner-per-property rule, and the
+  factory contract: each factory opens a **fresh, isolated** store
+  instance (no shared state between rows) with **idempotent
+  teardown**; engine factories for SQL engines skip cleanly when no
+  server is reachable (the alkstore SKIP posture) while acceptance
+  requires green against the server.
+- **The invariant backlog**: store-api.md's seven invariants
+  registered as the rows-to-grow table (round-trips per engine/tier/
+  put-path; dedup; stage hygiene; sweep safety incl. the engine-gated
+  fleet form; list-correctness-through-sweep-outcomes; `stat`-without-
+  content; engine-conformance uniformity) — each row's first column
+  lands with the mem engine in wave 2 (mem is the contract-reference
+  engine; every other engine's rows mirror its column).
+- **The harness skeleton**: the factory trait shape and the row
+  registration structure, compile-able as a stub (the `Store` facade
+  type arrives in wave 2 — the skeleton pins the shape, wave 2's
+  first column binds it; if binding reveals a shape correction, that
+  is wave 2's to make and record).
+
+This task is deliberately convention-first: the harness shape is
+easier to grow row by row as engines land than to retrofit onto five
+finished engines (the alkstore wave-1 rationale, which applies
+identically here).
+
+## Acceptance Criteria
+
+- [ ] `tests/conformance/` exists with the convention doc (row naming,
+      ADR-stamp format, one-owner rule, factory isolation + teardown
+      contract, SKIP posture)
+- [ ] The invariant backlog table registered, traceable to
+      store-api.md's seven invariants, with the mem-first column plan
+      noted
+- [ ] The harness skeleton compiles (`cargo test` green — a stub with
+      no rows yet is acceptable and expected)
+- [ ] No engine-specific code; the task adds no dependencies
+
+## References
+
+- docs/architecture/store-api.md (§Invariants — the test gate)
+- docs/architecture/backends-and-dispatch.md (§Per-engine conformance; POC #7 gate as the norm)
+- /workspace/@alkdev/alkstore/docs/plans/implementation.md (wave 1 + wave 5 sections — the convention's source pattern)
+- docs/plans/implementation.md (Decided points — suite home)
+
+## Notes
+
+> To be filled by implementation agent
+
+## Summary
+
+> To be filled on completion