ocaml: phase 5.1 island_count.ml baseline (6x7 grid, 5 components)

Count 4-connected components of 1-cells via DFS flood from every
unvisited 1-cell.

Grid (1s shown as #):
  # # . . . # #
  # . . . # # .
  . . # # . . .
  . # # # . # #
  # . . . . # .
  # # . # # # .

Components:
  {(0,0),(0,1),(1,0)}
  {(0,5),(0,6),(1,4),(1,5)}
  {(2,2),(2,3),(3,1),(3,2),(3,3)}
  {(3,5),(3,6),(4,5),(5,3),(5,4),(5,5)}
  {(4,0),(5,0),(5,1)}
                              -> 5 islands

Complementary to flood_fill.ml (largest component); this counts
total components.

Tests recursive function returning () at early-exit branches,
ordered double-for entry pass triggering one fill per island root.

180 baseline programs total.

lib/ocaml/baseline/expected.json

@@ -80,6 +80,7 @@
   "huffman.ml": 224,
   "int_sqrt.ml": 1027,
   "is_prime.ml": 25,
+  "island_count.ml": 5,
   "fizz_classifier.ml": 540,
   "fizzbuzz.ml": 57,
   "flatten_tree.ml": 28,