fix(persistence): reconcile project session layout

docs/config-catalog.md

@@ -978,9 +978,9 @@ export interface Config {
   /**
    * Root directory for all session files. Required (no default): a default of
    * `process.cwd()` would scatter session files as the process's cwd changes
-   * (bash calls, subprocesses). Sessions group under per-cwd subdirectories. An
-   * existing root must be a readable directory; an absent root is created on
-   * first materialization.
+   * (bash calls, subprocesses). Sessions group under human-readable project
+   * directories, then per-session directories. An existing root must be a
+   * readable directory; an absent root is created on first materialization.
    */
   root: string
   /**