feat(board): add Card detail supplement slot

docs/implementation-notes/card-execution-supplement.md

@@ -0,0 +1,52 @@
+# Card execution supplement
+
+Date: 2026-07-31
+
+## Intent
+
+`jtype-board-react` hosts such as jcode Cloud need to show execution receipts
+next to a Card without replacing the native Card editor. The package now exposes
+an additive `renderCardSupplement(card)` slot for that purpose.
+
+The host owns the supplement content and data. jtype continues to own Card
+title, description, status, properties, relations, comments, save behavior, and
+optimistic concurrency.
+
+## Public contract
+
+- `JTypeBoardProps.renderCardSupplement?: (card: BoardViewCard) => ReactNode`
+- The slot renders after native Properties and Relations in the built-in
+  editable Card detail.
+- It does not render for the explicit `readOnly` detail.
+- It does not render when `onCardOpen` intercepts the built-in detail.
+- Omission is a no-op.
+
+The slot flows through the shared component contract:
+
+`JTypeBoard → BoardSurface.renderCardSupplement → BoardPeek.supplement`.
+
+There are no Desktop/Web/Cloud platform conditionals.
+
+## Feature impact matrix
+
+| Surface | Behavior | Verification |
+| --- | --- | --- |
+| Desktop board | No change when the slot is omitted | Desktop build + shared board tests |
+| Web board | No change when the slot is omitted | Web build + shared board tests |
+| Editable `jtype-board-react` embed | Native editor plus optional host supplement | Package Playwright fixture |
+| Read-only package embed | Existing non-mutating detail; no supplement | Package Playwright fixture |
+| `onCardOpen` host | Host callback remains the only detail owner | Package Playwright fixture |
+| Package API/artifact | New prop exported in `.d.ts`; bundle and README updated | Package build/typecheck |
+
+## Test cases
+
+1. The editable package detail retains Description and Properties and adds the
+   host supplement.
+2. The read-only package detail does not render the editable supplement.
+3. `onCardOpen` interception does not render the supplement.
+4. Existing package editor tests continue to cover Card mutations and bounded
+   host layout.
+
+## Release
+
+Package version: `0.1.2`.

packages/board-react/README.md

@@ -43,6 +43,7 @@ The wrapper fills its container — **give the parent element a height.**
 | `live` | `boolean` | `true` | Try the live SSE feed; see *Live updates* below. |
 | `pollIntervalMs` | `number` | `30000` | Polling cadence (min 5000). |
 | `onCardOpen` | `(card: BoardViewCard) => void` | — | Intercept card opens; replaces the built-in read-only detail panel. |
+| `renderCardSupplement` | `(card: BoardViewCard) => ReactNode` | — | Add host-owned content after native Properties and Relations in the built-in editable Card detail. It is not rendered for `readOnly` or intercepted opens. |
 | `onConnectionChange` | `(s: 'live' \| 'polling' \| 'error') => void` | — | Observe transport state transitions. |
 | `locale` | `'en' \| 'zh' \| 'ja' \| 'ko'` | `'en'` | Board chrome language. The lingui instance is bundle-wide, so multiple boards on one page share the last-set locale. |
 | `className`, `style` | | — | Extra class/style for the wrapper element. |
@@ -142,7 +143,9 @@ read-only card detail, and localized chrome. Editable embeds use the shared
 focused quick-create and card-detail dialogs, including description,
 properties, relations, and sub-cards. Explicitly read-only embeds keep the
 non-mutating detail; a host `onCardOpen` callback still replaces either
-built-in path.
+built-in path. Hosts that need execution receipts or other contextual data
+without replacing the editor can use `renderCardSupplement`. The slot is
+additive: jtype retains ownership of Card editing and mutations.
 Not yet (flag-gated later): members/assignee options, versions/activity,
 ticket badges (the `OCCSV-####` chip — the embed client has no ticket-index
 endpoint, so cards never show it even when the board configures `ticketKey`),

packages/board-react/dist/index.d.ts

@@ -1,5 +1,6 @@
 import { CSSProperties } from 'react';
 import { ReactElement } from 'react';
+import { ReactNode } from 'react';
 
 /** Shape of the `.board` JSON config document (mirrors WebBoardView). */
 export declare type BoardConfigJSON = BoardDocumentConfig;
@@ -165,7 +166,7 @@ export declare class JTypeApiError extends Error {
  * `client`) plus `workspaceId`+`boardRef` and it renders the same shared
  * BoardSurface the jtype desktop + web apps use, backed by the document API.
  */
-export declare function JTypeBoard({ workspaceId, boardRef, baseUrl, token, client: injectedClient, readOnly, currentUser, live, pollIntervalMs, onCardOpen, onConnectionChange, locale, className, style, }: JTypeBoardProps): ReactElement;
+export declare function JTypeBoard({ workspaceId, boardRef, baseUrl, token, client: injectedClient, readOnly, currentUser, live, pollIntervalMs, onCardOpen, renderCardSupplement, onConnectionChange, locale, className, style, }: JTypeBoardProps): ReactElement;
 
 export declare type JTypeBoardConnection = 'live' | 'polling' | 'error';
 
@@ -235,6 +236,11 @@ export declare type JTypeBoardProps = {
     pollIntervalMs?: number;
     /** Intercept card opens (replaces the built-in editable/read-only detail). */
     onCardOpen?: (card: BoardViewCard) => void;
+    /**
+     * Add host-owned content after native Properties and Relations without
+     * replacing jtype's editor. Not rendered for read-only or intercepted opens.
+     */
+    renderCardSupplement?: (card: BoardViewCard) => ReactNode;
     /** Observe live/polling/error transitions. */
     onConnectionChange?: (state: JTypeBoardConnection) => void;
     /** Board chrome locale (default 'en'). Shared across instances (see README). */