docs: M5d-2 checklist: retain, Tally, mutation counts

Task 08 filters pending after the records walk so a ToolResult
before its ToolSummary is not summarised twice. Task 10 names
Tally to satisfy clippy type_complexity. Task 06 does not
return from tick when every_s is 0. README records 12/12
mutations caught.

Co-Authored-By: Grok 4.6 <noreply@x.ai>

docs/plans/M5d2/10-memoryd-tiers.md

@@ -88,6 +88,9 @@ listing. The starter `config/jobs/tier.toml.example` documents a weekly job; not
   `deny_unknown_fields` **off** so `epoch` and `query` do not fail.)
 - **Identity.** `store.entries(MemoryFile::Memory)` then `User`. Empty file: no identity
   lines for that file.
+- **Counts map.** A nested `HashMap<(String, i64), (u64, String)>` trips clippy
+  `type_complexity` (`-D warnings`). Name a small `Tally { n: u64, last: String }` and
+  return `HashMap<(String, i64), Tally>`. Do not `#[allow]`.
 - **`list` returns `Result<String, String>`.** Trailing newline on the last block is fine;
   `bxctl` adds another when printing `MemoryAdminReply.text` (`writeln!`). The given bxctl
   test includes a trailing newline in the reply text and expects it plus `writeln!`'s