SQLite engine integration: lint removal, contract-suite adoption, backlog column (task sqlite-engine-integration)

- Remove the wave-2 lint suppressions from substrate/mod.rs; the
  six genuinely dead surfaces the removal exposed are cut, not
  suppressed, and registered D-32..D-36 in PROVENANCE.md
  (arg_opt_i64, ops::now_unix, queue_next_claim_at,
  Writer::try_acquire, UpdateWatcher::spawn,
  SharedUpdateWatcher::new); test-observation items
  (subscriber_count, the poll-interval default re-export) are
  honestly #[cfg(test)]-gated
- Contract suite: eight new version-stamped backlog rows
  (extent-clamp + boundary totality, duration-refusal,
  encode_payload round-trip, PayloadTooLarge-never-produced SQLite
  arm, drop=rollback no-ghosts, in-tx read-your-own-writes,
  enqueue-opts resolution, receiver close/save arms)
- Fix the exemplar row's real-engine sequencing defect: the held tx
  handle across the with_tx leg deadlocked any single-writer factory
  (mock-invisible; ADR-007's parking is the pinned behavior)
- SQLite factory: SqliteFactory in the new tests/contract_suite.rs
  target; all nine rows green against it; the factory contract
  (isolation + idempotent teardown) pinned
- Engine lib docs: the single-host and writer-parking posture
  statements surfaced under # Posture
- Gates: build/test/clippy -D warnings/fmt green; coverage 93.6%
  lines, misses confined to error arms

alkstore-sqlite/src/substrate/mod.rs

@@ -40,32 +40,32 @@
 //! ops (`fork-rederive-queue-ops`, register D-12) live in
 //! `queue_ops.rs` — owned contract-v1 code, not lineage body.
 //!
-//! Port state (wave 2): the machinery below is ported; wave 3 wires
-//! `open` and the trait/seam impl. A subset of the ported surface
-//! remains unreachable until the mechanism tasks wire it (the
-//! `#![allow(dead_code)]` posture stays until the last wiring task).
-
-#![allow(dead_code)]
-#![allow(unused_imports)]
+//! Port state (wave 3): the machinery below is ported and wired — the
+//! engine layer reaches every substrate surface, so no dead-code
+//! posture remains; genuinely unreachable ported code is cut, not
+//! suppressed (any cut is a register entry in `PROVENANCE.md`).
 
 mod ops;
 mod queue_ops;
 mod schema;
 mod watcher;
 
+#[cfg(test)]
+pub(crate) use watcher::DEFAULT_WATCHER_POLL_INTERVAL;
+
 pub(crate) use ops::{
-    arg_i64, arg_opt_i64, attach_alkstore_functions, in_savepoint, lock_acquire, lock_release,
-    lock_renew, stream_get_offset, stream_publish, stream_read_since, stream_save_offset,
+    lock_acquire, lock_release, lock_renew, stream_get_offset, stream_publish, stream_read_since,
+    stream_save_offset,
 };
 pub(crate) use queue_ops::{
     FireOpts, Stamps, ack, ack_batch, cancel, claim_batch, enqueue, fail, get_job, heartbeat,
-    parse_every_interval, queue_next_claim_at, retry, scheduler_register, scheduler_soonest,
-    scheduler_tick, scheduler_unregister, sweep_expired,
-};
-pub(crate) use schema::{
-    Error as SchemaError, Readers, Writer, apply_default_pragmas, attach_notify, bootstrap_schema,
-    open_conn, open_conn_bootstrapped,
+    parse_every_interval, retry, scheduler_register, scheduler_soonest, scheduler_tick,
+    scheduler_unregister, sweep_expired,
 };
+pub(crate) use schema::Error as SchemaError;
+pub(crate) use schema::open_conn_bootstrapped;
+pub(crate) use schema::{Readers, Writer};
+pub(crate) use watcher::{SharedUpdateWatcher, WatcherConfig};
 
 /// Provision a fresh connection into the writer slot after a
 /// cancellation-path connection was consumed. Private helper over the
@@ -76,4 +76,3 @@ pub(crate) fn open_writer_connection(path: &str) -> Result<rusqlite::Connection,
         SchemaError::Sqlite(inner) => alkstore::Error::database(inner),
     })
 }
-pub(crate) use watcher::{DEFAULT_WATCHER_POLL_INTERVAL, SharedUpdateWatcher, WatcherConfig};