feat(ai-sdk): pin accepted proposer decisions into the GT gate (P3)

When a human accepts a proposer proposal, an AcceptedPin records a machine-scoped
invariant — a pattern MUST fire (coverage/vocab→tag) or must NOT fire
(dedup/framing) — that a test re-checks on every run. This makes the library's
growth COMPOUND into the gate instead of eroding it: a change that re-introduces
a dropped duplicate, un-gates a foreign pattern, or removes a coverage hazard
breaks a pin and fails CI. One boolean covers all four proposal types.

Seeded testdata/accepted_pins_warewashing.json with the accepted P1 supersessions
(HP016/HP018/HP013 must NOT fire; their clean equivalents HP2201/HP144 must fire).
TestWarewashing_AcceptedPins re-checks 5/5 against the live engine output;
GenerateDedupPin turns an accepted dedup verdict into its pin.

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

ai-compliance-sdk/internal/iace/proposer_pin.go

@@ -0,0 +1,73 @@
+package iace
+
+// P3: pin accepted proposer decisions into the GT gate.
+//
+// When a human accepts a proposal from the offline proposer (a dedup
+// supersession, a foreign-framing gate, a vocab→tag mapping, a coverage hazard),
+// they record an AcceptedPin. A pin is a tiny, machine-scoped invariant — "this
+// pattern MUST (or must NOT) fire for this machine" — that a test re-checks on
+// every run. This is what makes the library's growth COMPOUND into the gate
+// instead of silently eroding it: a future change that re-introduces a dropped
+// duplicate, un-gates a foreign pattern, or removes a coverage hazard breaks the
+// pin and fails CI.
+//
+// A single boolean covers all four proposal types:
+//   - dedup supersession accepted → DropPattern MustFire=false
+//   - foreign-framing gate accepted → foreign pattern MustFire=false
+//   - vocab→tag / coverage hazard accepted → the enabled pattern MustFire=true
+
+// AcceptedPin is one regression invariant for an accepted proposal.
+type AcceptedPin struct {
+	Pattern      string `json:"pattern"`
+	MustFire     bool   `json:"must_fire"`
+	Reason       string `json:"reason"`
+	FromProposal string `json:"from_proposal,omitempty"`
+}
+
+// PinSet is the accepted-pin registry for one machine (testdata/accepted_pins_*.json).
+type PinSet struct {
+	Machine string        `json:"machine"`
+	Pins    []AcceptedPin `json:"pins"`
+}
+
+// PinResult is the verdict for one pin against an engine run.
+type PinResult struct {
+	Pin    AcceptedPin
+	OK     bool
+	Detail string
+}
+
+// VerifyPins checks every pin against the set of pattern IDs the engine actually
+// fired for the machine. A pin holds iff the pattern's presence equals MustFire.
+func VerifyPins(pins []AcceptedPin, firedPatternIDs []string) []PinResult {
+	fired := make(map[string]bool, len(firedPatternIDs))
+	for _, id := range firedPatternIDs {
+		fired[id] = true
+	}
+	out := make([]PinResult, 0, len(pins))
+	for _, p := range pins {
+		got := fired[p.Pattern]
+		ok := got == p.MustFire
+		detail := "ok"
+		if !ok {
+			if p.MustFire {
+				detail = "expected to fire but did NOT — coverage/mapping regressed"
+			} else {
+				detail = "expected to be suppressed but FIRED — gate/supersession regressed"
+			}
+		}
+		out = append(out, PinResult{Pin: p, OK: ok, Detail: detail})
+	}
+	return out
+}
+
+// GenerateDedupPin turns an accepted (verdict=duplicate) dedup candidate into the
+// pin that protects the supersession: the dropped pattern must no longer fire.
+func GenerateDedupPin(c DedupCandidate) AcceptedPin {
+	return AcceptedPin{
+		Pattern:      c.DropPattern,
+		MustFire:     false,
+		Reason:       "accepted duplicate of " + c.KeepPattern + " (" + c.Category + ")",
+		FromProposal: "dedup " + c.DropPattern + " -> " + c.KeepPattern,
+	}
+}