Fold COASTAL_BATTERY into HOSTILE_ARTILLERY, it's the same thing

Same pattern already established for AMMO_CACHE -> SUPPLY_CACHE: a
'Coastal Battery' is just a heavy fixed-emplacement HostileArtillery
under a different name in the game's own text, not a meaningfully
different unit type worth its own enum member. Removed the
TargetType.COASTAL_BATTERY member, added 'CoastalBattery' to
ocr.py's _TYPE_WORD_ALIASES (so 'Coastal Battery#2:' still parses,
now as a HostileArtillery), and a models.py migration entry so any
save file written before this change still loads correctly.

Verified the migration directly (COASTAL_BATTERY -> HOSTILE_ARTILLERY,
existing AMMO_CACHE -> SUPPLY_CACHE unaffected) and updated the one
test that asserted the old type.

src/fenigma/models.py

@@ -41,10 +41,9 @@ class TargetType(Enum):
     FDC = "FDC"            # Fire Direction Center, coordinates enemy counter-battery fire
     INFANTRY = "Infantry"  # hostile ground troops
     MECHANIZED = "Mechanized"  # hostile armored/vehicle unit
-    HOSTILE_ARTILLERY = "Hostile Artillery"
+    HOSTILE_ARTILLERY = "Hostile Artillery"  # "Coastal Battery" is just this, see _TYPE_WORD_ALIASES in ocr.py
     HOSTILE_TANK = "Hostile Tank"
     PILLBOX = "Pillbox"    # armoured emplacement, fixed position
-    COASTAL_BATTERY = "Coastal Battery"  # heavy fixed emplacement, reported by listening posts
     MARINE_GARRISON = "Marine Garrison"  # allied unit, requests fire support (see Target.requested_time)
     ENEMY = "Enemy"        # ad-hoc installation named directly in the intel text
     # ("Enemy Signal Station", "Enemy Field Command"), not one of the
@@ -60,8 +59,9 @@ class TargetType(Enum):
 
 # Renamed/removed enum members, for loading save files written before the
 # rename. AMMO_CACHE turned out to be a misreading of the game's actual
-# "SupplyCache" name and was dropped in favor of it.
-_TARGET_TYPE_MIGRATIONS = {"AMMO_CACHE": "SUPPLY_CACHE"}
+# "SupplyCache" name and was dropped in favor of it. COASTAL_BATTERY
+# turned out to just be a HOSTILE_ARTILLERY under a different name.
+_TARGET_TYPE_MIGRATIONS = {"AMMO_CACHE": "SUPPLY_CACHE", "COASTAL_BATTERY": "HOSTILE_ARTILLERY"}
 
 
 def _migrate_target_type(name: str) -> TargetType:

src/fenigma/ocr.py

@@ -515,8 +515,10 @@ _BARE_CLUE_VALUE_RE = re.compile(
 
 _TYPE_BY_SHORT = {t.short: t for t in TargetType}
 # The game's typewriter has used "AmmoCache" for what's now modeled as
-# SupplyCache, treat it as the same type rather than dropping the target.
-_TYPE_WORD_ALIASES = {"AmmoCache": "SupplyCache"}
+# SupplyCache, and "CoastalBattery" for what's just a HostileArtillery
+# under a different name, treat both as the same type rather than
+# dropping the target or inventing a redundant enum member for it.
+_TYPE_WORD_ALIASES = {"AmmoCache": "SupplyCache", "CoastalBattery": "HostileArtillery"}
 
 
 _REF_NAMED_RE = re.compile(rf"^{_TYPE_ID_FRAGMENT}")