polish: six fixes from skill-migration reviews

Three minor-issues + three optional follow-ups identified by
the three parallel reviewers of debug/docwriter/audit,
fieldtest/planner/brainstorm, and implement. None blocking;
all close calibrated gaps the bulk migration left.

Minor-issues:
- audit/SKILL.md: handoff field `regression_results` now
  explicitly carries "raw output verbatim (no rounding, no
  summarisation)" — restores the verbatim-numbers emphasis
  the original `bench_numbers` field name implied.
- audit/agents/bencher.md: hypothesis examples grouped by
  axis (Tail-latency / Count reduction / Scalability /
  Overhead vs floor) with concrete numerical anchors (2× of
  median, ≥80%, 10-million-element, ±15%). Subjects stay
  domain-neutral but the calibrated bite returns. The
  preamble enumerates plausible subjects (allocators, query
  plans, request handlers, parsing strategies, codecs,
  caches) so the reader has concrete domains to anchor on.
- implement/agents/implementer.md: "Architecture rules"
  section gains a 5-bullet kind-list (determinism contracts;
  backend / FFI constraints; schema versions; memory /
  resource models; effect / capability discipline) so the
  implementer has scaffolding to look for even when the
  project's CLAUDE.md is sparse. The "BLOCKED on
  contradiction" mechanism stays the load-bearing rule.

Optional follow-ups:
- brainstorm/SKILL.md Step 7.5: failure-mode procedure
  restores the structured backlog-issue fields (Title /
  Label / Body with `depends on:` and `context:` lines)
  and the milestone-container option for big deferred work
  (Gitea milestones, GitHub milestones, Linear projects).
- templates/CLAUDE.md.fragment: adds an optional
  "Lockstep-invariant pairs" section so projects that have
  cross-file pairings can declare them in a way the
  architect agent and plan-recon agent already know to
  consult. Projects without such pairings omit the section;
  both agents handle absence gracefully.

No discipline regressions; no Iron Law / Common Rationalisations
/ Red Flags edits. Pure scaffold-and-anchor improvements.

brainstorm/SKILL.md

@@ -259,16 +259,33 @@ Orchestrator interpretation:
 1. Delete the just-written spec file from the working tree
    (`rm <spec_path>` — a shell delete on the working tree,
    NOT `git rm`; the file was never committed).
-2. Open a backlog issue (via the command configured under
-   `git.issue_tracker.list_cmd`'s sibling create command —
-   typically `tea issues create` for Gitea, `gh issue create`
-   for GitHub) pointing forward to a future re-brainstorm,
-   under the appropriate priority bucket.
+2. Open a backlog issue (via the project's issue-tracker
+   create command — `tea issues create` for Gitea,
+   `gh issue create` for GitHub, analogous for Linear /
+   Jira / etc.) pointing forward to a future re-brainstorm.
+   Include in the issue:
+
+   - **Title:** one-line identity of the deferred work
+   - **Label:** matching the project's vocabulary (often
+     `feature` / `bug` / `idea`; promote to `BLOCKER` if
+     the unratified mechanism is on a core-functionality
+     path)
+   - **Body:** short description, plus two structured
+     lines:
+     - `depends on: <name of the unratified mechanism>`
+     - `context: <why this is deferred>`
+
+   If the deferred work is large enough to need its own
+   spec on resumption — multi-iteration scope, cross-
+   subsystem — file it as a **milestone container**
+   instead (Gitea milestones, GitHub milestones, Linear
+   projects, whatever the project's tracker calls a
+   long-running work scope), not as a single issue.
 
 3. Tell the user the spec was retired and which backlog
-   issue was filed (include the issue number). No commit is
-   needed for the backlog entry — the issue tracker is the
-   live store.
+   entry was filed (include the issue or milestone number).
+   No commit is needed for the backlog entry — the issue
+   tracker is the live store.
 
 After the failure-mode procedure runs, the brainstorm
 session ENDS. There is no Step 8, no Step 9. The idea is