Fix P0 regression: explicit agent.cash in 3 test packs

Root cause is the same per-player cash plumbing regression that hit
test_resource_economy: PlayerSetup.cash defaults to 0, and an unset
agent.cash silently zeros out the pack-level starting_cash. With
agent.cash=0 the build queue can't consume cash, items.len grows
while remaining_cost never decreases (production stalls).

Patched all 3 P0 tests with explicit agent.cash matching the pack's
declared starting_cash:
* test_parallel_production: agent.cash=60000 (was 60000 top-level)
* test_pbox_fires (both base + _BUILD_PACK): cash=1000 / 2000
* test_repair_building_id: agent.cash=5000

All 5 sub-tests now pass:
test_two_war_factories_outproduce_one PASSED
test_preplaced_pbox_kills_in_range_enemy_e1 PASSED (was passing)
test_built_pbox_kills_enemy_e1 PASSED
test_stall_without_pbox_in_range_does_not_kill PASSED (was passing)
test_repair_via_real_building_id_heals_damaged_proc PASSED

tests/test_parallel_production.py

@@ -42,7 +42,7 @@ _PACK_YAML = textwrap.dedent(
     base_map: rush-hour-arena
     starting_cash: 60000
     base:
-      agent: {faction: allies}
+      agent: {faction: allies, cash: 60000}
       enemy: {faction: soviet, cash: 0}
       tools: [build, observe]
       spawn_mcvs: false

tests/test_pbox_fires.py

@@ -55,7 +55,7 @@ _PREPLACED_PACK = textwrap.dedent(
     base_map: rush-hour-arena
     starting_cash: 1000
     base:
-      agent: {faction: allies}
+      agent: {faction: allies, cash: 1000}
       enemy: {faction: soviet, cash: 0}
       tools: [observe]
       spawn_mcvs: false
@@ -104,7 +104,7 @@ _BUILD_PACK = textwrap.dedent(
     base_map: rush-hour-arena
     starting_cash: 2000
     base:
-      agent: {faction: allies}
+      agent: {faction: allies, cash: 2000}
       enemy: {faction: soviet, cash: 0}
       tools: [observe, build, place_building]
       spawn_mcvs: false

tests/test_repair_building_id.py

@@ -48,7 +48,7 @@ _PACK_YAML = textwrap.dedent(
     base_map: rush-hour-arena
     starting_cash: 5000
     base:
-      agent: {faction: allies}
+      agent: {faction: allies, cash: 5000}
       enemy: {faction: soviet, cash: 0}
       tools: [observe, repair]
       spawn_mcvs: false