feat(agents): Dispatch and supervise coding agents over ACP (#72)

## What

An Agents feature: hand a task to a coding agent and follow it from the IDE. Agents speak the [Agent Client Protocol](https://agentclientprotocol.com). Built in: Claude Code, Codex, Gemini CLI, GitHub Copilot, Cursor, OpenCode, Qwen Code, Kimi CLI, Goose, Auggie, Kiro, Mistral Vibe. You can add your own in `<config>/agents/<id>.toml` (`name`, `command`, `args`, `[env]`). An agent whose command isn't on `PATH` is listed under "Not installed".

- **New Task page.** An editor page with a prompt box. You pick the agent, model, mode and thinking effort, and whether it runs in a new worktree (from a chosen branch) or in the checkout.
- **Agents tool window.** Tasks are grouped by what they need: Needs Input, Failed, Running, Ready to Review, Archived. It also shows a stripe badge, a status bar item and notifications.
- **Session tab.**
  - The conversation: Markdown, thinking, tool calls with diff stats, the plan.
  - Permission requests appear as an editor banner.
  - The changed files are compared against the task's base commit and open in the diff viewer.
  - A context-usage meter.
- **Composer.**
  - `@` references files from the project index. A referenced file's text is sent when the agent accepts embedded context, otherwise a `resource_link`.
  - `/` lists the agent's commands; ↑/↓ recall earlier messages.
  - Images can be pasted, dropped or picked; Shift+Tab cycles the mode.
  - While the agent works, Enter queues the message and ⌘↵ interrupts the turn and sends it now. Queued messages can be sent now, edited or removed.
- **Send to Agent.** In the editor and Project view context menus. It adds `@file:10-20` references to the message you typed last.
- Landing the work is left to the existing Git features: the worktree is a normal branch.

## How

- **`crates/ide-agent`**: one ACP agent process per task, running in the task's directory.
  - It folds `session/update` into a timeline and answers `session/request_permission`.
  - It tracks the session's settings: `configOptions`, falling back to the older `modes` / `models` fields. The user's choices are applied again on every new or reloaded session.
  - Tasks are saved as JSON per task. Sessions resume with `session/load` without duplicating history, and old task files are upgraded when read.
- **`ide-jsonrpc`**: adds newline-delimited framing (ACP) next to Content-Length (LSP).
- **`ide-vcs`**: adds `numstat_with_worktree` for the changes list.
- **Editor**:
  - The Switcher (⌃⇥) lists every open editor, as IDEA does, not just files.
  - `EditorKindContribution.restorable` lets a kind's tabs be saved with the editor session, so agent tabs survive reloads.
- **UI**: `Select` popups now size to fit short option details (they used to cut them off).

## Testing

- `cargo test -p ide-agent` (14 tests). They use an in-memory ACP agent and cover permissions, restart with `session/load`, settings, the queue with send-now and stop, and prompt blocks.
- There is also an ignored end-to-end test against the real Claude Code adapter: `OPENIDEA_AGENT_E2E=1 cargo test -p ide-agent real_claude -- --ignored`.
- `pnpm vitest run`: 2052 tests.
- `cargo clippy -p ide-agent -p openidea --all-targets -- -D warnings` and typecheck are clean.
- Driven in the running app with Claude Code:
  - A task in a worktree, with permission answers, changes listed and the diff opened.
  - A follow-up after restarting the IDE.
  - `@` reference with embedded content, `/` commands, Shift+Tab mode changes.
  - A queued message and send-now, an image prompt, Send to Agent from a selection.
  - The Switcher and restored tabs after a reload.

Not covered yet: only Claude Code was driven end to end. The other agents go through the same ACP path but weren't run here.


Merged on the maintainer's go-ahead. Merge with main: kept both sides in Cargo.toml (ide-agent + ide-clipboard), the feature registry (agents + vim) and zh.json (no duplicate keys). After the merge: typecheck clean, full vitest 268 files / 2247 tests passed, ide-agent/ide-jsonrpc/ide-vcs 144 passed, bindings unchanged after regeneration.

src/editor/core/controller.ts

@@ -21,11 +21,13 @@ import {
   menuGroupItems,
   notifications,
   resolveFileEditor,
+  useContributions,
   type EditorInput,
   type OpenOptions,
+  type OpenEditorTab,
 } from "@/workbench/contributions";
 import { useDistractionFree } from "@/workbench/distractionFree";
-import { showContextMenu, type MenuItem } from "@/ui";
+import { fileIconName, showContextMenu, type MenuItem } from "@/ui";
 import { usePlatform } from "@/platform/platformInfo";
 import {
   activateTab,
@@ -140,6 +142,32 @@ function isTextTab(tab: Tab | null | undefined): tab is Tab & { input: { path: s
   return !!tab && isTextInput(tab.input);
 }
 
+type EditorKinds = ReturnType<typeof useContributions.getState>["editorKinds"];
+
+/** Tab title of an editor input: the file name, or what its editor kind calls it. */
+export function tabTitle(input: EditorInput, kinds: EditorKinds): string {
+  if (input.kind === "file") return basename(input.path ?? input.key);
+  if (input.kind === "virtual")
+    return (input.data as VirtualInputData | undefined)?.title ?? basename(input.path ?? input.key);
+  const kind = kinds.get(input.kind);
+  try {
+    return kind?.title(input) ?? input.key;
+  } catch {
+    return input.key;
+  }
+}
+
+export function tabIcon(input: EditorInput, kinds: EditorKinds): string {
+  if (input.kind === "file") return fileIconName(basename(input.path ?? ""));
+  if (input.kind === "virtual") return fileIconName(tabTitle(input, kinds));
+  const kind = kinds.get(input.kind);
+  try {
+    return kind?.icon?.(input) ?? "file";
+  } catch {
+    return "file";
+  }
+}
+
 export class EditorController implements SlotHost {
   manager: DocumentManager;
   readonly slots = new Map<string, EditorSlot>();
@@ -157,6 +185,9 @@ export class EditorController implements SlotHost {
   private restoredViews = new Map<string, FileViewState>();
   /** Tabs created by session restore; dropped silently if their file is gone. */
   private restoredTabs = new Set<string>();
+  /** When each input key was last the active tab (a counter, across panes). */
+  private lastActive = new Map<string, number>();
+  private activeClock = 0;
 
   constructor(backend: DocBackend = docBackend(), scheduler?: Scheduler) {
     this.manager = new DocumentManager(
@@ -178,6 +209,7 @@ export class EditorController implements SlotHost {
       useTabs.subscribe((s) => {
         const prev = prevTabs;
         prevTabs = s;
+        this.stampActive(s);
         this.onTabsChanged(prev, s);
       }),
     );
@@ -301,7 +333,8 @@ export class EditorController implements SlotHost {
       if (files[path] && slot.model.lastFocused !== slot && !this.restoredViews.has(path)) continue;
       files[path] = slot.viewState();
     }
-    storeSession(root, serializeSession(useTabs.getState(), files));
+    const kinds = useContributions.getState().editorKinds;
+    storeSession(root, serializeSession(useTabs.getState(), files, (input) => !!kinds.get(input.kind)?.restorable));
   }
 
   /** Reopens the tabs, splits and carets saved for `root` (after the project opened). */
@@ -993,6 +1026,29 @@ export class EditorController implements SlotHost {
     pane?.querySelector<HTMLElement>("[data-editor-focus], .cm-content")?.focus({ preventScroll: true });
   }
 
+  private stampActive(s: TabsState) {
+    const pane = s.panes[s.activePane];
+    const key = pane?.tabs.find((t) => t.id === pane.active)?.input.key;
+    if (key && this.lastActive.get(key) !== this.activeClock) this.lastActive.set(key, ++this.activeClock);
+  }
+
+  /** Every open tab once (all panes), most recently active first; tabs never active this session follow in tab order. */
+  openTabs(): OpenEditorTab[] {
+    const s = useTabs.getState();
+    const kinds = useContributions.getState().editorKinds;
+    const out = new Map<string, OpenEditorTab>();
+    for (const id of paneIds(s))
+      for (const t of s.panes[id]?.tabs ?? [])
+        if (!out.has(t.input.key))
+          out.set(t.input.key, {
+            input: t.input,
+            title: tabTitle(t.input, kinds),
+            icon: tabIcon(t.input, kinds),
+            lastActive: this.lastActive.get(t.input.key) ?? 0,
+          });
+    return [...out.values()].sort((a, b) => b.lastActive - a.lastActive);
+  }
+
   openPaths(): string[] {
     const s = useTabs.getState();
     const out = new Set<string>();