Harden quick-add against review findings

Independent review of the quick-add range surfaced real holes:

- The emptyLabel guard suppressed creation for any name that happened
  to be a substring of the label — typing "Rent" in the parent picker
  (a substring of "No parent (root)") silently offered nothing. The
  guard is gone; the exact-match rule already suppresses creates when
  the full label is typed.
- Async creates resolved against click-time snapshots, so a checkbox
  toggled or chip removed during the server round trip was silently
  reverted. Consumers now apply functional updates or a latest-value
  ref.
- Created names are capped at 200 characters, matching the registry
  forms; over-long text fails inline instead of minting a permanent
  multi-kilobyte name.
- A create failing after the user blurred mid-flight reopens the list
  so the error is never invisible, and option rows are locked while a
  create is in flight so a race cannot override an explicit pick.

web/src/Classification.tsx

@@ -695,6 +695,11 @@ function CorrectionEditor({
   mutate: Mutate;
   onChange: (value: CorrectionValue) => void;
 }) {
+  // Async creates resolve against the freshest correction, not the snapshot
+  // captured when the create row was clicked: a chip removed during the
+  // server round trip must survive the create landing.
+  const latest = useRef(value);
+  latest.current = value;
   const addable = data.tags
     .filter((t) => !value.tag_ids.includes(t.id))
     .map((t) => ({ value: t.id, label: t.name }));
@@ -739,7 +744,9 @@ function CorrectionEditor({
               mutate={mutate}
               value={value.category_id}
               disabled={disabled}
-              onChange={(category_id) => onChange({ ...value, category_id })}
+              onChange={(category_id) =>
+                onChange({ ...latest.current, category_id })
+              }
             />
           </dd>
         </div>
@@ -783,14 +790,13 @@ function CorrectionEditor({
                         {
                           key: "tag",
                           label: `Create tag "${text}"`,
-                          run: async () =>
+                          run: async () => {
+                            const id = await createTag(mutate, data, text);
                             onChange({
-                              ...value,
+                              ...latest.current,
-                              tag_ids: [
+                              tag_ids: [...latest.current.tag_ids, id],
-                                ...value.tag_ids,
+                            });
-                                await createTag(mutate, data, text),
+                          },
-                              ],
-                            }),
                         },
                       ]
                 }

web/src/Transactions.tsx

@@ -460,7 +460,9 @@ function TransactionEditor({
                 required
                 mutate={mutate}
                 value={value.category_id || ""}
-                onChange={(category_id) => setValue({ ...value, category_id })}
+                onChange={(category_id) =>
+                  setValue((v) => ({ ...v, category_id }))
+                }
               />
             </Field>
           )}
@@ -473,7 +475,7 @@ function TransactionEditor({
           <TagPicker
             data={data}
             value={value.tag_ids}
-            onChange={(tag_ids) => setValue({ ...value, tag_ids })}
+            onChange={(tag_ids) => setValue((v) => ({ ...v, tag_ids }))}
             mutate={mutate}
           />
           <details open>

web/src/ui.tsx

@@ -179,6 +179,9 @@ export function Combobox({
       setOpen(false);
     } catch (err) {
       setCreateError(err instanceof Error ? err.message : String(err));
+      // A blur may have closed the list mid-flight; a failure must never
+      // land invisibly.
+      setOpen(true);
     } finally {
       setCreating(false);
     }
@@ -208,7 +211,11 @@ export function Combobox({
           setActive(-1);
           setOpen(true);
         }}
-        onBlur={() => setOpen(false)}
+        onBlur={() => {
+          // A blur during an in-flight create keeps the list mounted so the
+          // outcome (or the error row) stays visible.
+          if (!creating) setOpen(false);
+        }}
         onKeyDown={(e) => {
           if (e.key === "Escape") setOpen(false);
           if ((e.key === "ArrowDown" || e.key === "ArrowUp") && open && total) {
@@ -250,6 +257,7 @@ export function Combobox({
                 }
                 role="option"
                 aria-selected={o.value === value}
+                disabled={creating}
                 onMouseDown={(e) => e.preventDefault()}
                 onClick={() => pick(o.value)}
               >
@@ -565,6 +573,8 @@ export async function createTag(
   data: Dataset,
   name: string,
 ): Promise<string> {
+  if (name.length > 200)
+    throw new Error("Tag names are limited to 200 characters.");
   const next = await mutate(
     "/api/tags",
     { tag: { id: "", name, hint: "" } },
@@ -582,6 +592,8 @@ export async function createCategory(
   data: Dataset,
   category: { name: string; parent_id: string; kind: string },
 ): Promise<string> {
+  if (category.name.length > 200)
+    throw new Error("Category names are limited to 200 characters.");
   const next = await mutate(
     "/api/categories",
     { category: { id: "", hint: "", ...category } },
@@ -610,6 +622,11 @@ export function TagPicker({
   const [draft, setDraft] = useState("");
   const [busy, setBusy] = useState(false);
   const [error, setError] = useState("");
+  // The async add resolves against the freshest selection, not the one
+  // captured at click time: a checkbox toggled during the server round trip
+  // must survive the create landing.
+  const latest = useRef(value);
+  latest.current = value;
   const add = async () => {
     const name = draft.trim();
     if (!name || busy || !mutate) return;
@@ -626,7 +643,7 @@ export function TagPicker({
     setError("");
     try {
       const id = await createTag(mutate, data, name);
-      onChange([...value, id]);
+      onChange([...latest.current, id]);
       setDraft("");
     } catch (err) {
       setError(err instanceof Error ? err.message : String(err));
@@ -756,10 +773,7 @@ export function CategoryCombobox({
     return data.categories.some((c) => pathOf(c.id) === full);
   };
   const create = (text: string): ComboCreate[] => {
-    // Text aiming at the empty option ("No parent…") is a selection, not a
+    if (!mutate) return [];
-    // new category name.
-    if (!mutate || emptyLabel?.toLowerCase().includes(text.toLowerCase()))
-      return [];
     const segments = text
       .split("/")
       .map((s) => s.trim())