feat: make each plugin an npm workspace built by a termix-plugin CLI

plugins/ai/src/frontend/index.mjs

@@ -0,0 +1,68 @@
+/**
+ * Frontend half of the ai plugin.
+ *
+ * AiPanel and the rest of src/ui/features/ai/ stay in core rather than
+ * moving here: TerminalAiPanel.tsx and TerminalProposalCard.tsx in
+ * src/ui/features/terminal/ (also core) import AiMessage, AiToolCall,
+ * useAiStream and ProposalCard directly, for the terminal's own docked AI
+ * panel. That is a real external dependency, the same reason session-manager
+ * stays in core for ssh-terminal rather than being copied into that plugin.
+ *
+ * The "ai" surface itself is not registered through registerTabComponent:
+ * it is a rail-view/right-dock panel baked into AppShell.tsx and
+ * tabUtils.tsx (railView === "ai", case "ai"), the same way the terminal's
+ * tab is baked into Terminal.tsx rather than going through the generic tab
+ * registry. What gates it is isTabTypeAvailable("ai") in
+ * src/ui/shell/pluginLoader.ts's BUILT_IN_TABS_BY_PLUGIN map.
+ *
+ * What this file DOES contribute is the terminal toolbar's AI button, through
+ * the action registry: ai.openWithContext, declared in manifest.json and
+ * gated on ai.services.use. The button used to be hardwired into
+ * TerminalToolbar.tsx behind a showAiAssistant prop.
+ *
+ * There is still no frontend plugin loader, so nothing imports this file yet
+ * (see src/ui/tests/sidebar/plugin-extension-seam.test.tsx). Until one exists,
+ * pluginLoader.ts performs the same registration itself when the ai plugin is
+ * enabled. This file is the version that runs once a loader lands, and the two
+ * must be kept in step.
+ */
+
+export const id = "ai";
+export const tabId = "ai";
+export const actionId = "ai.openWithContext";
+
+/** Asks the focused terminal to open its AI panel seeded with `context`. */
+export function openWithContext(context) {
+  window.dispatchEvent(
+    new CustomEvent("termix:ai:openWithContext", {
+      detail: { context: typeof context === "string" ? context : "" },
+    }),
+  );
+}
+
+export async function register({
+  registerAction,
+  registerSlotContribution,
+  icons,
+}) {
+  registerAction(actionId, openWithContext, {
+    permission: "ai.services.use",
+    pluginId: id,
+  });
+
+  registerSlotContribution("terminal.toolbar", {
+    actionId,
+    titleKey: "ai.assistant",
+    icon: icons.Bot,
+    kind: "button",
+    pluginId: id,
+  });
+}
+
+export async function unregister({
+  unregisterAction,
+  unregisterSlotContribution,
+}) {
+  unregisterSlotContribution("terminal.toolbar", actionId);
+  unregisterAction(actionId);
+}