chore(ui): refactor workspace to monorepo (#70)

## Summary by Sourcery

Refactor the UI project structure into a pnpm monorepo packages layout
and align tooling and automation with the new paths.

Enhancements:
- Reorganize the UI app from the root ui directory into packages/ui
within a pnpm workspace.
- Update pnpm workspace configuration to include all packages under
packages/*.
- Adjust paths in changeset configuration so the @dropout/ui package
resolves from packages/ui.

Build:
- Update pre-commit configuration paths and arguments to reflect the new
UI location and normalize hook argument formatting.
- Update Dependabot configuration so npm updates target /packages/ui
instead of /ui.

CI:
- Update GitHub Actions workflows to watch packages/** instead of ui/**
and to run frontend tasks from packages/ui.
- Update pnpm cache dependency paths in workflows to use the root
pnpm-lock.yaml.
- Simplify frontend install steps in test workflows to run from the
repository root.

Chores:
- Add a new index.html under packages/ui and remove the old
ui/index.html to match the new project layout.

1 files changed, 166 insertions, 0 deletions

diff --git a/packages/ui/src/stores/assistant.svelte.ts b/packages/ui/src/stores/assistant.svelte.ts
new file mode 100644
index 0000000..a3f47ea
--- /dev/null
+++ b/packages/ui/src/stores/assistant.svelte.ts
@@ -0,0 +1,166 @@
+import { invoke } from "@tauri-apps/api/core";
+import { listen, type UnlistenFn } from "@tauri-apps/api/event";
+
+export interface GenerationStats {
+  total_duration: number;
+  load_duration: number;
+  prompt_eval_count: number;
+  prompt_eval_duration: number;
+  eval_count: number;
+  eval_duration: number;
+}
+
+export interface Message {
+  role: "user" | "assistant" | "system";
+  content: string;
+  stats?: GenerationStats;
+}
+
+interface StreamChunk {
+  content: string;
+  done: boolean;
+  stats?: GenerationStats;
+}
+
+// Module-level state using $state
+let messages = $state<Message[]>([]);
+let isProcessing = $state(false);
+let isProviderHealthy = $state(false);
+let streamingContent = "";
+let initialized = false;
+let streamUnlisten: UnlistenFn | null = null;
+
+async function init() {
+  if (initialized) return;
+  initialized = true;
+  await checkHealth();
+}
+
+async function checkHealth() {
+  try {
+    isProviderHealthy = await invoke("assistant_check_health");
+  } catch (e) {
+    console.error("Failed to check provider health:", e);
+    isProviderHealthy = false;
+  }
+}
+
+function finishStreaming() {
+  isProcessing = false;
+  streamingContent = "";
+  if (streamUnlisten) {
+    streamUnlisten();
+    streamUnlisten = null;
+  }
+}
+
+async function sendMessage(
+  content: string,
+  isEnabled: boolean,
+  provider: string,
+  endpoint: string,
+) {
+  if (!content.trim()) return;
+  if (!isEnabled) {
+    messages = [
+      ...messages,
+      {
+        role: "assistant",
+        content: "Assistant is disabled. Enable it in Settings > AI Assistant.",
+      },
+    ];
+    return;
+  }
+
+  // Add user message
+  messages = [...messages, { role: "user", content }];
+  isProcessing = true;
+  streamingContent = "";
+
+  // Add empty assistant message for streaming
+  messages = [...messages, { role: "assistant", content: "" }];
+
+  try {
+    // Set up stream listener
+    streamUnlisten = await listen<StreamChunk>("assistant-stream", (event) => {
+      const chunk = event.payload;
+
+      if (chunk.content) {
+        streamingContent += chunk.content;
+        // Update the last message (assistant's response)
+        const lastIdx = messages.length - 1;
+        if (lastIdx >= 0 && messages[lastIdx].role === "assistant") {
+          messages[lastIdx] = {
+            ...messages[lastIdx],
+            content: streamingContent,
+          };
+          // Trigger reactivity
+          messages = [...messages];
+        }
+      }
+
+      if (chunk.done) {
+        if (chunk.stats) {
+          const lastIdx = messages.length - 1;
+          if (lastIdx >= 0 && messages[lastIdx].role === "assistant") {
+            messages[lastIdx] = {
+              ...messages[lastIdx],
+              stats: chunk.stats,
+            };
+            messages = [...messages];
+          }
+        }
+        finishStreaming();
+      }
+    });
+
+    // Start streaming chat
+    await invoke<string>("assistant_chat_stream", {
+      messages: messages.slice(0, -1), // Exclude the empty assistant message
+    });
+  } catch (e) {
+    console.error("Failed to send message:", e);
+    const errorMessage = e instanceof Error ? e.message : String(e);
+
+    let helpText = "";
+    if (provider === "ollama") {
+      helpText = `\n\nPlease ensure Ollama is running at ${endpoint}.`;
+    } else if (provider === "openai") {
+      helpText = "\n\nPlease check your OpenAI API key in Settings.";
+    }
+
+    // Update the last message with error
+    const lastIdx = messages.length - 1;
+    if (lastIdx >= 0 && messages[lastIdx].role === "assistant") {
+      messages[lastIdx] = {
+        role: "assistant",
+        content: `Error: ${errorMessage}${helpText}`,
+      };
+      messages = [...messages];
+    }
+
+    finishStreaming();
+  }
+}
+
+function clearHistory() {
+  messages = [];
+  streamingContent = "";
+}
+
+// Export as an object with getters for reactive access
+export const assistantState = {
+  get messages() {
+    return messages;
+  },
+  get isProcessing() {
+    return isProcessing;
+  },
+  get isProviderHealthy() {
+    return isProviderHealthy;
+  },
+  init,
+  checkHealth,
+  sendMessage,
+  clearHistory,
+};