fix(game): #59 — per-command rejection on PUT /api/v1/order

Validation of a player's order now applies every command against a
transient game-state snapshot and records the per-command outcome
(cmdApplied, cmdErrorCode) in each command's meta. The order is
persisted even when some commands are rejected, and the response is
202 + UserGamesOrder so clients can surface the partial failure
without the chain collapsing into "downstream service is unavailable".

Pkg/error consts are reshelved onto three explicit ranges with a
package doc and helpers (IsInternalCode/IsInputCode/IsGameStateCode):
1xxx internal/server (500/501), 2xxx structural input (400), 3xxx
game-state per-command rejection (400 when escaping HTTP, otherwise
recorded as cmdErrorCode). Two pre-existing typos fixed mechanically
(ErrBeakGroupNumberNotEnough -> ErrBreakGroupNumberNotEnough,
ErrRaceExinct -> ErrRaceExtinct) along with all callsites.

Engine errorResponse maps *GenericError by shelf rather than mapping
everything to 500. The Quit-not-last structural check in
Controller.ValidateOrder is preserved and its type assertion fixed
(was a value assertion against a pointer-typed command, so the check
silently never fired).

Backend, gateway and UI are unchanged — they were already correct on
the 202 path; only the engine collapsing per-command rejection into
500 was needed.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

game/internal/controller/fleet_test.go

@@ -37,7 +37,7 @@ func TestShipGroupJoinFleet(t *testing.T) {
 		e.GenericErrorText(e.ErrInputUnknownRace))
 	assert.ErrorContains(t,
 		g.ShipGroupJoinFleet(Race_Extinct.Name, fleetOne, groupIndex),
-		e.GenericErrorText(e.ErrRaceExinct))
+		e.GenericErrorText(e.ErrRaceExtinct))
 
 	// ensure race has no Fleets
 	assert.Len(t, slices.Collect(c.ListFleets(Race_0_idx)), 0)
@@ -124,14 +124,14 @@ func TestFleetMerge(t *testing.T) {
 		e.GenericErrorText(e.ErrInputUnknownRace))
 	assert.ErrorContains(t,
 		g.FleetMerge(Race_Extinct.Name, fleetSourceOne, fleetTargetTwo),
-		e.GenericErrorText(e.ErrRaceExinct))
+		e.GenericErrorText(e.ErrRaceExtinct))
 
 	assert.ErrorContains(t,
 		g.ShipGroupJoinFleet(UnknownRace, fleetSourceOne, c.ShipGroup(0).ID),
 		e.GenericErrorText(e.ErrInputUnknownRace))
 	assert.ErrorContains(t,
 		g.ShipGroupJoinFleet(Race_Extinct.Name, fleetSourceOne, c.ShipGroup(0).ID),
-		e.GenericErrorText(e.ErrRaceExinct))
+		e.GenericErrorText(e.ErrRaceExtinct))
 
 	assert.NoError(t, g.ShipGroupJoinFleet(Race_0.Name, fleetSourceOne, c.ShipGroup(0).ID))