simplify(seams): prune dead methods from the persistence and bash seams

Two capability seams carried abstract methods no production consumer calls.
A method no consumer programs against is not a seam — it is speculative
surface every implementation must still provide and test.

- SessionPersistence: remove has() and delete(), the coordinator's
  has/delete/deleteCore, and the PersistenceBackend.deleteStored hook (with its
  jsonl + sqlite + in-spec memory-stub impls). Surviving service surface:
  create/append/load/list. Production uses only load() (resume) and list()
  (ACP session/list).
- BashExecutor: remove get(id) and list(), the abstract decls and the
  LocalBashExecutor impls. The internal tasks map survives (it backs
  ownerOf/readOutput/kill); get/list were pure public accessors over it with no
  shipping caller and no bash_list tool.
- Migrate tests that reached through ctx.bash.get(id) to the public completion
  seam: a doneFor(id) helper over onTaskDone awaits a task by id, and the
  HMR-reload ownership test now proves task survival through A's own bash_output
  ([status: running]) plus ownerOf + B-rejection — a stronger through-the-tool
  assertion than the removed lookup peek.
- Update seam READMEs (six -> four service methods, drop the deleteStored hook
  and the get/list row) and the two implemented persistence RFCs in place.

Implements docs/rfc/implemented/simplification/2026-06-20-prune-dead-seam-methods.md

packages/session-persistence/session-persistence-sqlite/src/index.ts

@@ -11,7 +11,7 @@
  * Like the JSONL backend it supplies ONLY the storage primitives (the
  * {@link PersistenceBackend} hooks below — INSERT/DELETE/SELECT inside
  * transactions); all the write-path orchestration lives in the backend-agnostic
- * {@link PersistenceCoordinator} this class composes. The six public
+ * {@link PersistenceCoordinator} this class composes. The four public
  * {@link SessionPersistence} methods delegate to the coordinator.
  *
  * @module @deepseek-ai/dsh-session-persistence-sqlite
@@ -99,14 +99,6 @@ export class SessionPersistenceSqlite extends SessionPersistence implements Pers
     return this.coordinator.load(id)
   }
 
-  has(id: SessionId): Promise<boolean> {
-    return this.coordinator.has(id)
-  }
-
-  delete(id: SessionId): Promise<void> {
-    return this.coordinator.delete(id)
-  }
-
   // `list` is BOTH the public service method and the PersistenceBackend hook —
   // one method (the SELECT below). The coordinator adds no orchestration for
   // listing, so routing it through the coordinator would just recurse. Defined
@@ -203,12 +195,6 @@ export class SessionPersistenceSqlite extends SessionPersistence implements Pers
     }
   }
 
-  /** Remove a session's row (ON DELETE CASCADE drops its events). */
-  async deleteStored(id: SessionId): Promise<void> {
-    await this.ready
-    this.db.prepare('DELETE FROM sessions WHERE id = ?').run(id)
-  }
-
   /** List all materialized sessions' metadata (every row is a materialized session). */
   async list(): Promise<SessionHeader[]> {
     await this.ready
@@ -234,7 +220,7 @@ export class SessionPersistenceSqlite extends SessionPersistence implements Pers
   /**
    * Insert-or-replace a session's metadata row. The only caller is the first
    * materializing `appendBatch`, so writing the row IS the materialization (its
-   * existence is the signal `has`/`list` read).
+   * existence is the signal `list` reads).
    */
   private writeRow(meta: SessionHeader): void {
     this.db.prepare(`

packages/session-persistence/session-persistence-sqlite/src/schema.ts

@@ -21,7 +21,7 @@ export const SCHEMA_VERSION = 2
  * A row of the `sessions` table — the out-of-log metadata ({@link SessionHeader}).
  * The row's EXISTENCE is the materialization signal: it is written only by the
  * first `append` (lazy materialization), so a created-but-never-appended
- * session has no row and is absent from `has`/`list`, mirroring the JSONL
+ * session has no row and is absent from `list`, mirroring the JSONL
  * backend's "no file until first append".
  */
 export interface SessionRow {