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.

implement/agents/implementer.md

@@ -95,11 +95,29 @@ is yes — write the test.
 
 The binding architectural rules of the project are declared
 in `CLAUDE.md` and (if the project has one) the design
-ledger at `paths.design_ledger`. Read them as part of the
-standing reading list. Respect them in the diff. If the
-task text appears to ask for something a binding rule
-forbids, return `BLOCKED` with the contradiction named — do
-not silently substitute.
+ledger at `paths.design_ledger`. The specific rules are
+project-specific, but they typically cover:
+
+- **Determinism contracts.** Canonical forms, sort orders,
+  hash schemes, anything where the project commits to a
+  fixed byte-level output.
+- **Backend / foreign-function constraints.** Which library
+  calls are forbidden, which are required, which version
+  is pinned.
+- **Schema / format versions.** What `v0` / `v1` shapes
+  are, what counts as a breaking change, what migration
+  notes a schema bump requires.
+- **Memory / resource models.** Reference counting,
+  ownership, lifetime invariants, capacity bounds.
+- **Effect / capability discipline.** What functions may
+  perform IO / network / unsafe, how effect annotations
+  flow.
+
+Read the project's rules as part of the standing reading
+list. Respect them in the diff. If the task text appears
+to ask for something a binding rule forbids, return
+`BLOCKED` with the contradiction named — do not silently
+substitute.
 
 ## The Process