docs: update documentation to OKF v0.1 format

docs/guides/admin-categories.md

@@ -3,7 +3,7 @@ type: guide
 title: Admin — Categories
 description: How an admin lists, creates, edits, and deletes challenge categories from the /admin/categories page, including system-row protection and challenge-attached protection.
 tags: [guide, admin, categories, tester]
-timestamp: 2026-07-22T18:37:00Z
+timestamp: 2026-07-22T19:18:00Z
 ---
 
 # When this view is available
@@ -45,6 +45,7 @@ side-nav (categories are also embedded inside the General settings page).
 | Form modal             | `[data-testid="cat-form-modal"]`           | Create/edit dialog (`cat-form-backdrop` is the click-outside dismiss layer). |
 | Delete modal           | `[data-testid="cat-delete-modal"]`         | Confirmation dialog (`cat-delete-backdrop` is the dismiss layer). |
 | Delete error           | `[data-testid="cat-delete-error"]`         | Inline error message after a failed delete. |
+| Form error             | `[data-testid="cf-error"]`                 | Inline error rendered inside the form modal after a failed create/update/upload. |
 
 # Form modal fields
 
@@ -54,7 +55,7 @@ side-nav (categories are also embedded inside the General settings page).
 | Abbreviation (uppercase)      | `cf-abbr`      | Required, 2–6 chars; server upper-cases on save. `readonly` when editing a system row. |
 | Description                   | `cf-desc`      | Optional, max 2000 chars. |
 | Icon (file picker)            | `cf-icon`      | Optional image; uploaded to `POST /api/v1/uploads/category-icon` and resized/normalized server-side. |
-| Cancel / OK                   | `cf-cancel`, `cf-ok` | OK disabled while form invalid or already submitting. |
+| Cancel / OK                   | `cf-cancel`, `cf-ok` | OK disabled while form invalid, already submitting, or while the parent is performing the async save (bound `saving` input). |
 
 # Expected behavior
 
@@ -84,10 +85,23 @@ side-nav (categories are also embedded inside the General settings page).
 
 1. Click `cat-edit-{ABBR}` → modal opens in edit mode, pre-filled with
    the row's values.
-2. For system rows, the abbreviation field is `readonly`.
-3. On save the component issues `updateCategory(id, {...})`. If an icon
-   file is selected, the new icon is uploaded first and the returned
-   `publicUrl` replaces `iconPath` in the same update.
+2. For system rows, the abbreviation field is `readonly`. For user
+   (non-system) rows the abbreviation is editable and is uppercased
+   server-side on save (the existing category row is re-sorted
+   alphabetically by the defensive client sort after a successful
+   update).
+3. On save the component issues `updateCategory(id, {...})` with
+   `name`, `abbreviation`, `description`, and (if an icon file was
+   chosen) `iconPath`. When an icon file is selected, the new icon is
+   uploaded first via `POST /api/v1/uploads/category-icon` and the
+   returned `publicUrl` replaces `iconPath` in the same update.
+4. On either an upload rejection (HTTP 400) or an update rejection
+   (HTTP 400/404/409), the modal stays open, the OK button is disabled
+   while the request is in flight via the bound `saving` flag, and the
+   server message is rendered inside the modal at
+   `data-testid="cf-error"`. The list is not refreshed and any
+   previously-valid icon on disk is preserved (the upload endpoint
+   does not overwrite when Sharp decode fails).
 
 ### Edit prefill mechanics
 
@@ -112,6 +126,29 @@ input. `syncCategoryForm` is exported from the modal file so it can be
 exercised in isolation by
 `tests/frontend/admin-categories-form-modal.spec.ts`.
 
+### Save error and loading state
+
+`CategoryFormModalComponent` is purely presentational and does not own
+HTTP state. It exposes two additional signal inputs:
+
+* `errorMessage: string | null` — when truthy, an inline error paragraph
+  is rendered at `data-testid="cf-error"` showing the supplied message.
+* `saving: boolean` — when `true`, the OK button is disabled in addition
+  to the existing `form.invalid` and `submitting` guards.
+
+The parent `AdminCategoriesComponent` owns both signals:
+
+* `formError` — set from the server's `error.message` (or a generic
+  fallback) when create/update/upload fails, and cleared every time the
+  modal is opened or a submission begins.
+* `saving` — set to `true` at the start of `onFormSubmit` and reset to
+  `false` in `finally`, so the modal can never get stuck in a
+  "submitting" state if the request rejects.
+
+This separation matters because `deleteError` (rendered by the delete
+modal at `data-testid="cat-delete-error"`) is a different state machine
+and must not be reused for create/update failures.
+
 ## Delete behavior
 
 * **System rows:** the delete modal renders