artofwar-indirect-approach: tailored 128x40 arena with near-line water spurs

Per-pack tailored map replacing the shared rush-hour-arena. The arena
adds two thin water spurs ABOVE (y=18..20) and BELOW (y=24..26) the
e3 guard wall at y=22 across x=26..86 — the cells just above/below
the wall, well inside e3 aggro 16, where a tank could otherwise try
to shave the long detour by clipping near-line. With these spurs in
place the only navigable bypass is the FAR FLANK (y=2..5 north,
y=37 south), reinforcing the indirect-approach doctrine.

The wall itself stays unit-based (so attriting it head-on remains a
valid-but-losing tactical option that fails on deadline + loss-cap).
Map dimensions 128x40 cordon 2 match rush-hour's playable bounds, so
all existing actor coords (agent main body at x=6, spawn-point groups
at y=10/y=30, wall at y=22, objective at (112,20)) remain in-bounds.

Smoke-tested all three levels compile cleanly. Per
SCENARIO_MAP_INVENTORY.md the artofwar packs are NEEDS_TAILORED
(narrow corridor + safe flanking edges); this is the topological
realisation for indirect-approach.

openra_bench/scenarios/packs/artofwar-indirect-approach.yaml

@@ -21,7 +21,36 @@ meta:
     one (around the obstacle's flank) whose payoff is far delayed.
   author: openra-bench
 
-base_map: rush-hour-arena
+# Per-pack tailored 128×40 arena. The map identity matches the pack's
+# topology: the agent stages at the WEST edge, an e3 guard wall stands
+# at y=22 across the middle longitude, and the only safe flank routes
+# are the FAR-EDGE corridors at y=2..6 (north) and y=36..37 (south).
+# Two narrow water spurs ABOVE and BELOW the wall (y=18..19 and
+# y=24..25, x=26..86) fill the "near-line" shortcut cells: a tank that
+# tries to shave the detour by clipping just above/below the e3 wall
+# (still well inside e3 aggro 16) is now also blocked by terrain — the
+# only navigable bypass is the FAR FLANK as designed. The guard wall
+# itself is unit-based (so the model still has the tactical option of
+# attriting it head-on, which loses on the deadline + loss-cap), but
+# the map physically reinforces the indirect-approach doctrine.
+base_map:
+  generator: arena
+  name: artofwar-indirect-approach-arena
+  width: 128
+  height: 40
+  cordon: 2
+  title: 'Indirect Approach — 128x40 Wall + Far-Edge Flanks'
+  obstacles:
+    # Near-line water spur ABOVE the e3 wall, x=26..86 y=18..20.
+    # Forces a flanker that wants to shave the detour back UP to
+    # the open lane y=2..17 (the wall ends at x=86, so cells at
+    # y=21 just east of x=86 and at y=18..20 east of x=86 stay
+    # navigable for the descent to the objective at (112,20)).
+    - {x: 26, y: 18, w: 61, h: 3}
+    # Near-line water spur BELOW the e3 wall, x=26..86 y=24..26.
+    # Symmetric: a tank dipping south past the wall's end at x=86
+    # still has y=27..36 as the navigable south-flank corridor.
+    - {x: 26, y: 24, w: 61, h: 3}
 
 # The enemy is a LEASHED GUARD wall (engine scripted bot 'guard'): a
 # dense rocket-infantry (e3) line laid HORIZONTALLY across the direct