feat: Show error toast when concurrency limit is reached

When a user tries to drag a card from backlog to in_progress while at the
max concurrency limit, a toast notification now appears explaining why the
action was blocked and suggesting solutions.

- Added sonner toast library
- Show error toast with dynamic message based on max concurrency
- Updated test utilities with toast helpers

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.automaker/feature_list.json

@@ -1,53 +1,70 @@
 [
-  {
-    "id": "feature-1765252193603-eb6fx2zcy",
-    "category": "UI",
-    "description": "change the description in add new feature modal to a textarea",
-    "steps": [
-      "go to kanban view",
-      "click new feature button",
-      "verify description is textarea"
-    ],
-    "status": "verified"
-  },
-  {
-    "id": "feature-1765252237454-1gudpwx26",
-    "category": "Kanban",
-    "description": "change category to a typeahead and save the category of the feature inside the feature_list.json",
-    "steps": [],
-    "status": "verified"
-  },
-  {
-    "id": "feature-1765252262937-bt0wotam8",
-    "category": "Kanban",
-    "description": "Deleting a feature should show a confirm dialog",
-    "steps": [],
-    "status": "verified"
-  },
-  {
-    "id": "feature-1765252502536-t11kphnca",
-    "category": "Kanban",
-    "description": "If i have the output of a feature open while it's in progress, then it gets verified, automatically close the output modal",
-    "steps": [
-      "1. drag YOLO11 to in progress",
-      "2. open the output modal",
-      "3. wait until it is moved to verified",
-      "4. assert modal is hidden"
-    ],
-    "status": "verified"
-  },
-  {
-    "id": "feature-1765254432072-bqk25kivv",
-    "category": "Automode",
-    "description": "Add a concurrency slider left of automode so I can specify how many max agents should be running at one time.  if we are at max, do not pull over more tasks from the backlog",
-    "steps": [],
-    "status": "verified"
-  },
   {
     "id": "feature-1765259922422-d61lu00sq",
     "category": "Core",
     "description": "add a context feature / route which allows users to upload files or images or text which will persist to .automaker/context. there should be a left panel with all context files and a text editor or image previewer that lets users view edit delete the context.  include the context in every single coding prompt or improve the coding_prompt.md to have a phase where it loads in that context",
     "steps": [],
     "status": "in_progress"
+  },
+  {
+    "id": "feature-1765260287663-pnwg0wfgz",
+    "category": "Agent Runner",
+    "description": "When I archived a session I had selected, I'd expect it to unselect it",
+    "steps": [
+      "1. create a session",
+      "2. select it",
+      "3. archive it",
+      "4. expect empty state placeholder in right panel"
+    ],
+    "status": "backlog"
+  },
+  {
+    "id": "feature-1765260557163-86b3tby5d",
+    "category": "Core",
+    "description": "Remove analysis link and related code, it's not useful",
+    "steps": [],
+    "status": "backlog"
+  },
+  {
+    "id": "feature-1765260608543-frhplaxss",
+    "category": "Kanban",
+    "description": "when clicking a value in the typeahead, there is a bug where it does not close automatically, fix this",
+    "steps": [],
+    "status": "backlog"
+  },
+  {
+    "id": "feature-1765260671085-7dgotl21h",
+    "category": "Kanban",
+    "description": "show a error toast when concurrency limit is hit and someone tries to drag a card into in progress to give them feedback why it won't work.",
+    "steps": [],
+    "status": "verified"
+  },
+  {
+    "id": "feature-1765260791341-iaxxt172n",
+    "category": "Kanban",
+    "description": "Add a way to force stop an agent on a card which is currently running",
+    "steps": [],
+    "status": "in_progress"
+  },
+  {
+    "id": "feature-1765260864296-98yunv0vj",
+    "category": "Kanban",
+    "description": "Remove drag icon from cards when in in progress or verified.  also add a timer that tracks how long it has been since the agent started, a count up timer basically formatted 00:00",
+    "steps": [],
+    "status": "backlog"
+  },
+  {
+    "id": "feature-1765260912320-p7d5eang8",
+    "category": "Kanban",
+    "description": "add a count up timer for showing how long the card has been in progress",
+    "steps": [],
+    "status": "backlog"
+  },
+  {
+    "id": "feature-1765261027396-b78maajg7",
+    "category": "Kanban",
+    "description": "When the agent is marked as verified, remove their context file",
+    "steps": [],
+    "status": "backlog"
   }
 ]