feat(tests): the conformance suite's sqlite column — the durable-schedule SQL-backed column green (wave 3)

- The first SQL-backed column: the default-build production shape
  (kv = sqlite + large = local, feature sqlite default-on) runs the
  form-independent reference rows verbatim (INV-1, INV-6, the
  NoLivenessSources/ProtectFailed abort shapes, the kv-only rejection
  row against kv-only(sqlite)) and grows the durable-schedule sweep
  rows — exact counts asserted relative to the staged schedule
  (ADR-012 §6.7): two-sweep counts over the full protection set, the
  race across the window delay (a re-put landing during the window
  survives the executing sweep), the holder-stages-only lease shape,
  INV-5 through durable-schedule outcomes, and the schedule-relative
  INV-2/INV-3 readings
- Dispatch rows mirror the local column's family with the placement
  oracle adapted by medium: the sqlite file's pool/window rows vs the
  root's committed files; virgin-store reads as no-ops on a fresh file
  (the no-tables-yet tolerance engine-instrumented, this row its
  facade form)
- Factories: dual-tier sqlite+local and kv-only(sqlite), instance-
  tracked temp sites (fresh sqlite file + private root per open;
  idempotent panicking-row-safe teardown), the column-tuned threshold
  and the test window-delay tuning (Duration::ZERO — execute-on-next-
  sweep); the module is cfg(feature = "sqlite"), default-on — the
  column runs in every default cargo test, server-less, never skips
- Shared fixtures moved to rows.rs (committed_file_count,
  staging_file_count, slice_digest, LatchProtect pub(crate)) so the
  columns share them without the mem gate
- README: the schedule-relative reading for SQL-backed columns
  recorded (citing ADR-012 §6.7), the sqlite rows table inventory,
  Current state (three columns)

Verification: cargo test (default) green — 69 lib + 19 conformance +
3 git-interop; cargo test --features mem green (124 lib + 54
conformance); cargo check --all-features --tests green; cargo clippy
--all-targets -- -D warnings green; cargo fmt --check green.

tests/conformance/main.rs

@@ -25,7 +25,12 @@
 //! [`local_column`] — the suite's first dual-tier column (the
 //! `kv = mem` + `large = local` dispatch-coverage shape ADR-012 §6.3
 //! names), which mirrors the reference set and grows the
-//! dispatch-coverage and local-specific rows.
+//! dispatch-coverage and local-specific rows; [`sqlite_column`] — the
+//! suite's first SQL-backed column (the default-build production
+//! shape, `kv = sqlite` + `large = local`), which mirrors the
+//! form-independent reference rows and grows the durable-schedule
+//! sweep rows (README §The schedule-relative reading for SQL-backed
+//! columns).
 //!
 //! Items beyond the tests below are the later columns' surface, hence
 //! the scoped `#![allow(dead_code)]` — it shrinks as columns land.
@@ -41,6 +46,8 @@ mod local_column;
 #[cfg(feature = "mem")]
 mod mem_column;
 mod rows;
+#[cfg(feature = "sqlite")]
+mod sqlite_column;
 mod stamp;
 
 #[test]