SQLite engine open: SqliteOpts, connection architecture, spawn_blocking seam posture (task sqlite-engine-open-opts)

- SqliteOpts (poll_interval: Option<Duration>, None = 1 ms shipping
  default ADR-023 §4; max_readers, DEFAULT_MAX_READERS = 8; opts
  exemption from non_exhaustive per ADR-017 §3)
- open(path, opts) -> Box<dyn Store>: writer slot, reader pool,
  SharedUpdateWatcher with fallible spawn mapped W-2-style into
  Error::Database; plain-path posture (ADR-023 §3) pinned by test
- Substrate delta D-30: open_conn_bootstrapped — every connection
  (writer and pooled readers) carries the full bootstrap surface
  (pragmas, notify, alkstore functions, schema) per engine-sqlite.md;
  lineage opened readers pragmas-only. Registered in PROVENANCE.md
- spawn_blocking seam helper + error mappings (string/rusqlite ->
  Database, source chains preserved); helper cfg(test)-gated until
  sqlite-engine-seam-tx wires the trait impls
- Store trait stubbed with Database errors (no panics); close()/Drop
  join the watcher, clear subscribers (death-guard), close pool+writer
- 15 new tests (open boot, watcher fanout/death-close, cadence
  accounting, plain-path literal filename, :memory:, pool bounding,
  drop teardown, seam smoke incl. panic mapping); gates green

alkstore-sqlite/src/substrate/PROVENANCE.md

@@ -118,6 +118,7 @@ fixes. Cherry-picks: empty at scaffold, append-only forever.
 | D-27 | re-derivation | wave-2 review fix — `scheduler_tick`'s fire enqueue resolved the schedule row's relative `expires_s` into the absolute row `expires_at` (`now + s` at the fire transaction, one clock read) instead of passing the relative value through; regression test pins a fired job's `expires_at = fire-instant + s` and its claimability. The pre-fix pass-through would have produced rows expired in 1970 under any `expires_s` schedule | `queue_ops.rs` (`scheduler_tick`, fire-expiry resolution + test) | ADR-020 §2 (relative `expires` → resolved absolute row value, resolved at enqueue against the single clock) — D-12's landed state carried the lineage's `expires_s` field shape without carrying the lineage's enqueue-side resolution; wave-2 review (task review-wave-2) re-derivation spot-check found it | ours |
 | D-28 | hygiene | wave-2 review fix — the cross-mechanism pressure test's lock-churn branch exercised a per-producer lock name (literal `"p{producer}"` had no interpolation, so all producers contended on one name) with its result swallowed via `.unwrap_or(0)`; now interpolates, releases periodically, propagates errors | `ops.rs` (pressure test, lock branch) | test-quality only (no lineage counterpart, no library code touched); `fork-provenance-and-floor`'s ported-surface pressure intent | ours |
 | D-29 | port delta | `SQLITE_OPEN_URI` dropped from `open_conn`'s flags (the watcher's own opens never carried it — the inherited posture was internally inconsistent); the path argument is a plain filesystem path, `?name=value` suffixes are literal filenames, no connection-semantics mutation outside the engine constructor's opts; pinned by test (`open_conn_treats_uri_shaped_path_as_plain_filename`) | `schema.rs` (`open_conn`) | ADR-023 §3 (plain-path open — the URI parameter surface is SQLite's, not this engine's; no consumer-inventory row names URI features) | ours |
+| D-30 | port delta | `open_conn_bootstrapped` — new function stacking the engine's full per-connection open posture (pragmas, notify, `attach_alkstore_functions`, `bootstrap_schema`), and `Readers::acquire`'s open path switched from bare `open_conn` to it (fresh connections only — the pool never re-bootstraps a reused connection). The lineage's pools opened readers pragmas+notify only, the function set + schema living only on the writer; this engine's reader-slot operations (claim/ack, stream reads, lock ops, scheduler checks, leadership probes) run this substrate's SQL functions on pooled connections, so every pooled connection carries the full surface | `schema.rs` (`open_conn_bootstrapped`, `Readers::acquire` open path) | engine-sqlite.md's connection architecture ("each connection runs the substrate's bootstrap at open — the writer and each pooled reader") — engine-layer obligation of `sqlite-engine-open-opts`; landed with the engine's `open` wiring | ours |
 
 ### Cherry-picks