fix(pipeline,audit): gate-side floors for prose-only no-op guards

Two roll-ups were vacuously satisfiable by a no-op and guarded only in
agent prose, never re-verified at the consuming gate:

- The milestone-close functional leg trusted a fieldtest `clean` roll-up
  even from a run with zero examples. The gate now requires
  examples_added >= 2 for a `clean` to be honoured (the empty-report and
  internal-milestone escapes are preserved); a `clean` with fewer over
  user-visible surface is itself a `spec_gap`.
- The audit carry-on accepted an architect `clean` with no evidence of
  review. It now requires a non-empty "What holds" (added as an explicit
  handoff field); a bare `clean` with nothing held — worst when no
  regression scripts run, so the architect is the sole gate — reads as
  unreviewed and is re-dispatched.

Both are second-layer checks: the consumer verifies the field rather
than trusting the agent's discipline. Lower-severity defense-in-depth,
not code-level floors (milestone-close and audit carry-on are
orchestrator-judgment acts with no script to instrument).

closes #14

audit/SKILL.md

@@ -110,12 +110,23 @@ The orchestrator picks per item:
   commits always exist at cycle close — they carry the architect
   findings, the regression numbers, and the resolution.
 
+  A carry-on is honoured only with positive evidence the architect
+  actually reviewed: a non-empty **What holds** in its report (the
+  design commitments it confirmed it read). A bare `clean` with
+  nothing held — especially when Step 2 was a no-op (no regression
+  scripts, so the architect is the *sole* gate) — reads as an
+  unreviewed run, not a clean cycle; re-dispatch rather than close
+  on it. (The architect owes this itself — `agents/architect.md`
+  Red Flags, "about to return clean without having read the diff in
+  full"; the gate verifies it rather than trusting the status.)
+
 ## Handoff Contract
 
 `audit` hands to the orchestrator:
 
 | Field | Content |
 |-------|---------|
+| `holds` | architect's **What holds** — the 1-3 design commitments the cycle preserved (`agents/architect.md` Output format). Non-empty is the evidence-of-review the carry-on gate checks; an empty `holds` reads as an unreviewed run. |
 | `drift_items` | prioritised list (path + 1-line justification) from architect |
 | `regression_results` | per script: exit code + **raw output verbatim** (no rounding, no summarisation — the orchestrator second-guesses with the full numbers) |
 | `recommendation` | per-item: `fix` / `ratify` / `carry-on` |