Branching zones G7: collapse empty columns in !zone map

The graph-mode map renderer iterated 0..maxX, emitting a blank slot for
columns whose only inhabitant was a hidden secret node. In Matrix code
blocks the dark background painted that gap as a phantom cell with no
status mark — read in playtest as "a box missing a dot." Collapse
columns with no visible nodes before laying out rows; secret columns
reappear once the player visits them.

internal/plugin/zone_graph_map.go

@@ -57,9 +57,19 @@ func renderZoneGraphMap(g ZoneGraph, run *DungeonRun) string {
 		})
 	}
 
+	// Drop columns that have no visible nodes (e.g. when the only
+	// entry was a hidden secret). Otherwise the render leaves a blank
+	// slot mid-row that reads as a missing status mark.
+	visibleX := make([]int, 0, maxX+1)
+	for x := 0; x <= maxX; x++ {
+		if len(cols[x]) > 0 {
+			visibleX = append(visibleX, x)
+		}
+	}
+
 	// Find max stack height per column for vertical alignment.
 	maxRows := 0
-	for x := 0; x <= maxX; x++ {
+	for _, x := range visibleX {
 		if len(cols[x]) > maxRows {
 			maxRows = len(cols[x])
 		}
@@ -73,9 +83,9 @@ func renderZoneGraphMap(g ZoneGraph, run *DungeonRun) string {
 	var sb strings.Builder
 	for row := 0; row < maxRows; row++ {
 		var top, bot strings.Builder
-		for x := 0; x <= maxX; x++ {
-			if x > 0 {
-				connector, statusGap := graphConnector(g, cols[x-1], cols[x], row, visited)
+		for i, x := range visibleX {
+			if i > 0 {
+				connector, statusGap := graphConnector(g, cols[visibleX[i-1]], cols[x], row, visited)
 				top.WriteString(connector)
 				bot.WriteString(statusGap)
 			}

internal/plugin/zone_graph_map_test.go

@@ -58,6 +58,43 @@ func TestRenderZoneGraphMap_HidesUnvisitedSecrets(t *testing.T) {
 	}
 }
 
+// TestRenderZoneGraphMap_CollapsesEmptyColumns confirms columns whose
+// only inhabitant is a hidden secret don't leave a phantom blank slot
+// in the glyph/status rows. Prior to G7 the renderer iterated 0..maxX
+// and emitted a space for empty columns, which read as a "missing dot".
+func TestRenderZoneGraphMap_CollapsesEmptyColumns(t *testing.T) {
+	nodes := []ZoneNode{
+		{NodeID: "z.entry", Kind: NodeKindEntry, IsEntry: true, PosX: 0},
+		{NodeID: "z.mid", Kind: NodeKindExploration, PosX: 1},
+		// Secret sits alone in column 2 — hidden until visited.
+		{NodeID: "z.secret", Kind: NodeKindSecret, PosX: 2, PosY: 1},
+		{NodeID: "z.boss", Kind: NodeKindBoss, IsBoss: true, PosX: 3},
+	}
+	edges := []ZoneEdge{
+		{From: "z.entry", To: "z.mid"},
+		{From: "z.mid", To: "z.secret", Lock: LockPerception, LockData: map[string]any{"dc": 12}},
+		{From: "z.mid", To: "z.boss"},
+		{From: "z.secret", To: "z.boss"},
+	}
+	g := BuildGraph("test_zone_collapse", nodes, edges)
+	got := renderZoneGraphMap(g, &DungeonRun{
+		CurrentNode:  "z.entry",
+		VisitedNodes: []string{"z.entry"},
+	})
+	// With col 2 collapsed, the top row should be a contiguous chain
+	// E──?──☠ with no double-gap.
+	if !strings.Contains(got, "E──?──☠") {
+		t.Errorf("expected collapsed top row 'E──?──☠', got:\n%s", got)
+	}
+	// And no run of 3+ spaces between glyphs (would indicate a phantom column).
+	for _, line := range strings.Split(got, "\n") {
+		trimmed := strings.TrimSpace(line)
+		if strings.Contains(trimmed, "   ") {
+			t.Errorf("phantom empty column detected in line %q (full output:\n%s)", line, got)
+		}
+	}
+}
+
 // TestRenderZoneGraphMap_LockedEdgeRenderedAsCross verifies locked-only
 // approaches show ╳ instead of ──.
 func TestRenderZoneGraphMap_LockedEdgeRenderedAsCross(t *testing.T) {