feat(branches): add folder delete action and context menu

Add ability to delete all branches in a folder from the UI. Add a
handler to batch-delete local or remote branches and refresh views.

- Batch deletion handles remote and local branches and reports failures.
- Folder context menu receives branches and disables delete if needed.
- Track folder deletion attempts and failures via telemetry.

src/lib/components/BranchPanel.svelte

@@ -12,6 +12,7 @@
     children: BranchTreeNode[];
     branchCount: number;
     current: boolean;
+    branches: GitBranchInfo[];
     folders: Map<string, BranchFolderNode>;
   }
 
@@ -31,6 +32,7 @@
     depth: number;
     branchCount: number;
     current: boolean;
+    branches: GitBranchInfo[];
   }
 
   interface BranchLeafRow {
@@ -57,6 +59,7 @@
     onRenameBranch: (branch: GitBranchInfo) => void | Promise<void>;
     onDeleteBranch: (branch: GitBranchInfo) => void | Promise<void>;
     onDeleteRemoteBranch: (branch: GitBranchInfo) => void | Promise<void>;
+    onDeleteBranchFolder: (folderName: string, branches: GitBranchInfo[]) => void | Promise<void>;
     onCreateTag: (name: string, message: string) => void | Promise<void>;
     onDeleteTag: (tag: GitTag) => void | Promise<void>;
     onPushTag: (tag: GitTag) => void | Promise<void>;
@@ -81,6 +84,7 @@
     onRenameBranch = () => {},
     onDeleteBranch = () => {},
     onDeleteRemoteBranch = () => {},
+    onDeleteBranchFolder = () => {},
     onCreateTag = () => {},
     onDeleteTag = () => {},
     onPushTag = () => {},
@@ -101,6 +105,7 @@
   let newTagMessage = $state("");
   let tagCreateInput = $state<HTMLInputElement | null>(null);
   let contextBranch = $state<GitBranchInfo | null>(null);
+  let contextFolder = $state<BranchFolderRow | null>(null);
   let branchContextMenuElement = $state<HTMLElement | null>(null);
   let contextMenuX = $state(0);
   let contextMenuY = $state(0);
@@ -121,6 +126,7 @@
       children: [],
       branchCount: 0,
       current: false,
+      branches: [],
       folders: new Map(),
     };
   }
@@ -147,6 +153,7 @@
 
         folder.branchCount += 1;
         folder.current ||= branch.current;
+        folder.branches.push(branch);
         parent = folder;
       }
 
@@ -188,6 +195,7 @@
           depth,
           branchCount: node.branchCount,
           current: node.current,
+          branches: node.branches,
         });
 
         if (isBranchFolderOpen(node.id)) {
@@ -272,8 +280,25 @@
     contextMenuY = position.y;
   }
 
+  async function openFolderContextMenu(event: MouseEvent, folder: BranchFolderRow) {
+    event.preventDefault();
+    event.stopPropagation();
+    if (isBusy) return;
+
+    contextFolder = folder;
+    contextMenuX = event.clientX + 2;
+    contextMenuY = event.clientY + 2;
+    await tick();
+    if (contextFolder !== folder) return;
+
+    const position = fitContextMenuToViewport(branchContextMenuElement, event.clientX, event.clientY);
+    contextMenuX = position.x;
+    contextMenuY = position.y;
+  }
+
   function closeBranchContextMenu() {
     contextBranch = null;
+    contextFolder = null;
   }
 
   async function renameContextBranch() {
@@ -297,6 +322,13 @@
     if (branch.remote) await onDeleteRemoteBranch(branch); else await onDeleteBranch(branch);
   }
 
+  async function deleteContextFolder() {
+    const folder = contextFolder;
+    if (!folder || isBusy) return;
+    closeBranchContextMenu();
+    await onDeleteBranchFolder(folder.name, folder.branches);
+  }
+
   async function createContextWorktree() {
     const branch = contextBranch;
     closeBranchContextMenu();
@@ -484,6 +516,7 @@
                   style={`--branch-indent: ${row.depth * 16}px;`}
                   type="button"
                   onclick={() => toggleBranchFolder(row.id)}
+                  oncontextmenu={(event) => openFolderContextMenu(event, row)}
                   aria-expanded={isBranchFolderOpen(row.id)}
                   title={`${row.name} (${row.branchCount})`}
                 >
@@ -551,6 +584,7 @@
                   style={`--branch-indent: ${row.depth * 16}px;`}
                   type="button"
                   onclick={() => toggleBranchFolder(row.id)}
+                  oncontextmenu={(event) => openFolderContextMenu(event, row)}
                   aria-expanded={isBranchFolderOpen(row.id)}
                   title={`${row.name} (${row.branchCount})`}
                 >
@@ -735,6 +769,29 @@
     </div>
   {/if}
 
+  {#if contextFolder}
+    <div
+      bind:this={branchContextMenuElement}
+      class="branch-context-menu"
+      style={`left: ${contextMenuX}px; top: ${contextMenuY}px;`}
+      role="menu"
+      tabindex="-1"
+      aria-label={`Actions for branch folder ${contextFolder.name}`}
+    >
+      <button
+        class="danger"
+        type="button"
+        role="menuitem"
+        onclick={deleteContextFolder}
+        disabled={isBusy || contextFolder.branches.every((branch) => branch.current)}
+        title={contextFolder.current ? "The current branch will be kept" : "Delete all branches in this folder"}
+      >
+        <Trash2 size={14} aria-hidden="true" />
+        Delete {contextFolder.branches.filter((branch) => !branch.current).length} branches
+      </button>
+    </div>
+  {/if}
+
   {#if contextTag}
     <div
       bind:this={tagContextMenuElement}