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>

pkg/model/order/order.go

@@ -124,6 +124,7 @@ type CommandMeta struct {
 	CmdID      string      `json:"cmdId" binding:"required,uuid_rfc4122"`
 	CmdApplied *bool       `json:"cmdApplied,omitempty"`
 	CmdErrCode *int        `json:"cmdErrorCode,omitempty"`
+	CmdErrMsg  *string     `json:"cmdErrorMessage,omitempty"`
 }
 
 func (cm CommandMeta) CommandType() CommandType {
@@ -134,9 +135,18 @@ func (cm CommandMeta) CommandID() string {
 	return cm.CmdID
 }
 
-func (cm *CommandMeta) Result(errCode int) {
+// Result records the per-command outcome on the meta. errCode == 0 marks
+// the command as applied and clears CmdErrMsg; non-zero records the
+// rejection along with the human-readable engine message so clients can
+// surface the reason without their own code-to-text catalog.
+func (cm *CommandMeta) Result(errCode int, errMsg string) {
 	cm.CmdErrCode = &errCode
 	cm.CmdApplied = new(bool(errCode == 0))
+	if errCode == 0 {
+		cm.CmdErrMsg = nil
+		return
+	}
+	cm.CmdErrMsg = &errMsg
 }
 
 type CommandRaceQuit struct {