feat(ai-sdk): coverage blind-spot proposer (P2 slice 6, type 4)

Completes the proposer's four types.

- FindCoverageGaps (proposer_coverage.go): deterministic — which EN ISO 12100
  hazard groups A-G did the engine leave with zero hazards for this machine? An
  empty group is a structural blind-spot signal (the machine may truly lack it,
  or a pattern/GT case is missing). Useful with no model at all.
- ProposeMissingHazards + BuildCoveragePrompt: optional LLM expansion of each gap
  into specific expected-but-missing hazards a safety assessor would name
  (propose-only, reuses LLMCompleter, degrades to nil on any error).
- Wired into iace-audit propose -> audit-reports/coverage.{md,json}.

On the dishwasher: D. Pneumatik (truly absent — nothing invented), E. Laerm
(borderline), F. Ergonomie (a genuine gap: manual loading the engine did not
produce). P3 (pin an accepted proposal into a GT case) remains as a human-in-the-
loop follow-up.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

ai-compliance-sdk/cmd/iace-audit/propose.go

@@ -103,6 +103,15 @@ func cmdPropose(args []string) {
 	writeText("audit-reports/vocab.md", renderVocabQueue(in.MachineType, vgaps))
 	writeJSON("audit-reports/vocab.json", vgaps)
 
+	// Type 4: coverage blind-spots (empty ISO 12100 groups A-G) + LLM expansion.
+	gaps := iace.FindCoverageGaps(hazards)
+	var missing []iace.MissingHazard
+	if lj, ok := judge.(iace.LLMJudge); ok {
+		missing = iace.ProposeMissingHazards(ctx, lj.Completer, in.MachineType, in.Narrative, hazards, gaps)
+	}
+	writeText("audit-reports/coverage.md", iace.RenderCoverageQueue(in.MachineType, gaps, missing))
+	writeJSON("audit-reports/coverage.json", gaps)
+
 	printSummary("Method P — Dedup Proposer ("+judge.Name()+")", map[string]int{
 		"fired_patterns": len(fired),
 		"candidates":     len(candidates),
@@ -110,6 +119,7 @@ func cmdPropose(args []string) {
 		"gt_blocked":     blocked,
 		"framing_flags":  len(framing),
 		"vocab_gaps":     len(vgaps),
+		"coverage_gaps":  len(gaps),
 	})
 	if gt == nil {
 		fmt.Fprintln(os.Stderr, "note: no ground truth provided — GT wall NOT applied (candidates not recall-screened)")