J3 D8-f #2: T4 difficulty lift (leaders-define-band) + feywild fork1 soft-lock fix

T4 monster tuning so martial leaders land in the 60-75% band (underdark
59/80, feywild 65/84 at L10/L12, n=50); casters trail (class-side gap that
monster tuning provably can't compress -- Pass 1 showed casters pinned at 0%
while martials moved). T5 deferred (walls everyone at its L12 floor; needs an
L15-16 corpus).

- dnd_bestiary.go: underdark elite/boss HP+AC up + caster-lethal proc cuts
  (mind_flayer/drow_mage/roper); feywild HP+AC up.
- bestiary_srd.go: feywild multiattack profiles (fomorian/night_hag/green_hag)
  + Thornmother 2->3 lashes -- HP/AC alone didn't move feywild's low-damage
  roster; multiattack is what pulls facerolling martials into band.
- zone_graph_feywild_crossing.go: free fork1's marsh edge. fork1 was the only
  fork in the game with every exit skill-locked (CHA+Perception, no LockNone)
  and deterministic no-retry rolls -- a prod SOFT-LOCK stranding ~60% of
  players (low CHA+WIS). Kept grove's CHA bargain as a bonus route.
- expedition_sim.go: firstUnlockedForkChoice -- sim fork policy picks the
  first unlocked option instead of blind 'go 1' (which looped forever on
  locked forks); halts fork_all_locked if none.
- tests: graph-wide TestZoneGraphs_NoSoftLockedFork + fork1 free-path guard.

Writeup: sim_results/d8f_findings.md

internal/plugin/zone_graph_test.go

@@ -190,6 +190,40 @@ func TestCompileLegacyZoneGraph_AllRegistered(t *testing.T) {
 	}
 }
 
+// TestZoneGraphs_NoSoftLockedFork guards the invariant that every fork
+// node offers at least one traversable (LockNone) exit. A fork whose
+// every edge is skill-locked strands any player who fails all the checks
+// — fork rolls are deterministic with no retry. D8-f part 2 found
+// feywild fork1 violating this (it stranded ~60% of runs). Catch any
+// future author who locks every exit of a fork.
+func TestZoneGraphs_NoSoftLockedFork(t *testing.T) {
+	for _, z := range allZones() {
+		g, ok := loadZoneGraph(z.ID)
+		if !ok {
+			continue
+		}
+		for nodeID, node := range g.Nodes {
+			if node.Kind != NodeKindFork {
+				continue
+			}
+			outs := g.outgoingEdges(nodeID)
+			if len(outs) == 0 {
+				continue
+			}
+			free := false
+			for _, e := range outs {
+				if e.Lock == LockNone || e.Lock == "" {
+					free = true
+					break
+				}
+			}
+			if !free {
+				t.Errorf("zone %q fork %q: every exit is locked — soft-lock (a player failing all checks is stranded; add a LockNone fallback)", z.ID, nodeID)
+			}
+		}
+	}
+}
+
 func TestDeriveLegacyNodeID_StableShape(t *testing.T) {
 	got := deriveLegacyNodeID("crypt_valdris", 0)
 	want := "crypt_valdris.r1"