fix(order): surface rejection reason, keep sync green, hydrate verdicts

Three issues surfaced once the per-command rejection from the previous
commit actually reached the UI:

1. Sync banner falsely red. `OrderDraftStore.runSync` flipped
   `syncStatus = "error"` whenever any command was rejected and
   advertised a Retry button. A per-command rejection is a
   player-correctable state — the round trip succeeded, the engine
   just refused that command — so the retry can't help. Keep
   `syncStatus = "synced"` on `success`; the red row highlight is
   the visible cue.

2. Rejection reason missing. Add `cmd_error_message: string` to
   `CommandItem` in `pkg/schema/fbs/order.fbs` (appended last to
   preserve existing slot offsets) and regenerate the Go + TS stubs
   for that one type. Plumb the message through `CommandMeta`,
   `Controller.applyCommand`'s `m.Result(code, message)` call, the
   Go transcoder, the UI decoders in `submit.ts` /  `order-load.ts`,
   and the `OrderDraftStore.errorMessages` map. `order-tab.svelte`
   renders it as an italic danger-coloured line under rejected
   commands, with new CSS for `.error-reason`.

3. Verdict lost on navigation. `order-load.ts.decodeCommand` never
   read `cmdApplied`/`cmdErrorCode`, so `hydrateFromServer` fell
   back to a blanket "applied" status — a previously-rejected
   command came back green after a lobby → game round trip. Extend
   the fetch decoder to populate `statuses`/`errorCodes`/
   `errorMessages` maps and have `hydrateFromServer` use them.
   Engine-side persistence already records the verdict on disk —
   verified against the live `0000/order/<id>.json`.

`flatbuffers@25` elides default-int8/int64 fields on write; the Go
transcoder force-slots `cmd_applied=false` / `cmd_error_code=0`
already, the new test fixtures flip `builder.forceDefaults(true)` to
mirror that behaviour so the round trip survives.

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

ui/frontend/src/lib/sidebar/order-tab.svelte

@@ -153,6 +153,10 @@ Tests exercise the tab through `__galaxyDebug.seedOrderDraft`
 	function statusOf(cmd: OrderCommand): CommandStatus {
 		return draft?.statuses[cmd.id] ?? "draft";
 	}
+
+	function errorMessageOf(cmd: OrderCommand): string | null {
+		return draft?.errorMessages[cmd.id] ?? null;
+	}
 </script>
 
 <section class="tool" data-testid="sidebar-tool-order">
@@ -191,6 +195,7 @@ Tests exercise the tab through `__galaxyDebug.seedOrderDraft`
 		<ol class="commands" data-testid="order-list">
 			{#each draft.commands as cmd, index (cmd.id)}
 				{@const status = statusOf(cmd)}
+				{@const errorReason = errorMessageOf(cmd)}
 				<li
 					class="command status-{status}"
 					data-testid="order-command-{index}"
@@ -200,6 +205,14 @@ Tests exercise the tab through `__galaxyDebug.seedOrderDraft`
 					<span class="label" data-testid="order-command-label-{index}">
 						{describe(cmd)}
 					</span>
+					{#if status === "rejected" && errorReason !== null}
+						<span
+							class="error-reason"
+							data-testid="order-command-error-{index}"
+						>
+							{errorReason}
+						</span>
+					{/if}
 					<span
 						class="sr-only"
 						data-testid="order-command-status-{index}"
@@ -314,6 +327,16 @@ Tests exercise the tab through `__galaxyDebug.seedOrderDraft`
 		min-width: 0;
 		overflow-wrap: anywhere;
 	}
+	.error-reason {
+		grid-column: 2;
+		min-width: 0;
+		overflow-wrap: anywhere;
+		margin-top: 0.1rem;
+		color: var(--color-danger);
+		font-size: 0.75rem;
+		font-style: italic;
+		line-height: 1.25;
+	}
 	.banner {
 		margin: 0 0 0.5rem;
 		padding: 0.5rem 0.75rem;