feat: add Atlas PRD agent for product discovery

- src/prompts/atlas.ts — full Atlas system prompt (6-phase PM discovery flow)
- src/tools/prd.ts — finalize_prd tool that signals PRD completion
- src/agents/atlas.ts — Atlas agent config (Tier A, conversational)
- src/atlas.ts — atlasChat() multi-turn session handler
- server.ts — /atlas/chat, /atlas/sessions endpoints

Made-with: Cursor

src/atlas.ts

@@ -0,0 +1,159 @@
+import { createLLM, toOAITools, LLMMessage } from './llm';
+import { ALL_TOOLS, executeTool, ToolContext } from './tools';
+import { resolvePrompt } from './prompts/loader';
+import { prdStore } from './tools/prd';
+
+const MAX_TURNS = 10; // Atlas is conversational — low turn count, no deep tool loops
+
+// ---------------------------------------------------------------------------
+// Session store
+// ---------------------------------------------------------------------------
+
+interface AtlasSession {
+    id: string;
+    history: LLMMessage[];
+    prdContent: string | null;
+    createdAt: string;
+    lastActiveAt: string;
+}
+
+const sessions = new Map<string, AtlasSession>();
+
+function getOrCreateSession(sessionId: string): AtlasSession {
+    if (!sessions.has(sessionId)) {
+        sessions.set(sessionId, {
+            id: sessionId,
+            history: [],
+            prdContent: null,
+            createdAt: new Date().toISOString(),
+            lastActiveAt: new Date().toISOString()
+        });
+    }
+    const session = sessions.get(sessionId)!;
+    session.lastActiveAt = new Date().toISOString();
+    return session;
+}
+
+export function clearAtlasSession(sessionId: string): void {
+    sessions.delete(sessionId);
+}
+
+export function listAtlasSessions() {
+    return Array.from(sessions.values()).map(s => ({
+        id: s.id,
+        messages: s.history.length,
+        prdReady: s.prdContent !== null,
+        createdAt: s.createdAt,
+        lastActiveAt: s.lastActiveAt
+    }));
+}
+
+// ---------------------------------------------------------------------------
+// Atlas chat result
+// ---------------------------------------------------------------------------
+
+export interface AtlasChatResult {
+    reply: string;
+    sessionId: string;
+    history: LLMMessage[];
+    /** Set when Atlas has called finalize_prd — contains the full PRD markdown */
+    prdContent: string | null;
+    model: string;
+}
+
+// ---------------------------------------------------------------------------
+// Main chat handler
+// ---------------------------------------------------------------------------
+
+const ATLAS_TOOLS = ALL_TOOLS.filter(t => t.name === 'finalize_prd');
+
+export async function atlasChat(
+    sessionId: string,
+    userMessage: string,
+    ctx: ToolContext,
+    opts?: {
+        preloadedHistory?: LLMMessage[];
+    }
+): Promise<AtlasChatResult> {
+    const llm = createLLM(process.env.ATLAS_MODEL ?? 'A', { temperature: 0.5 });
+    const session = getOrCreateSession(sessionId);
+
+    // Seed from DB history if this is a fresh in-memory session
+    if (opts?.preloadedHistory && opts.preloadedHistory.length > 0 && session.history.length === 0) {
+        session.history = [...opts.preloadedHistory];
+    }
+
+    const oaiTools = toOAITools(ATLAS_TOOLS);
+    const systemPrompt = resolvePrompt('atlas');
+
+    session.history.push({ role: 'user', content: userMessage });
+
+    const buildMessages = (): LLMMessage[] => [
+        { role: 'system', content: systemPrompt },
+        ...session.history.slice(-60)
+    ];
+
+    let turn = 0;
+    let finalReply = '';
+    let prdContent: string | null = session.prdContent;
+
+    while (turn < MAX_TURNS) {
+        turn++;
+
+        const response = await llm.chat(buildMessages(), oaiTools, 4096);
+
+        const hasContent = response.content !== null && response.content !== '';
+        const hasToolCalls = response.tool_calls.length > 0;
+
+        if (hasContent || hasToolCalls) {
+            session.history.push({
+                role: 'assistant',
+                content: response.content,
+                tool_calls: hasToolCalls ? response.tool_calls : undefined
+            });
+        }
+
+        if (!hasToolCalls) {
+            finalReply = response.content ?? '';
+            break;
+        }
+
+        // Execute tool calls (only finalize_prd for Atlas)
+        for (const tc of response.tool_calls) {
+            let fnArgs: Record<string, unknown> = {};
+            try { fnArgs = JSON.parse(tc.function.arguments || '{}'); } catch { /* bad JSON */ }
+
+            let result: unknown;
+            try {
+                result = await executeTool(tc.function.name, fnArgs, ctx);
+            } catch (err) {
+                result = { error: err instanceof Error ? err.message : String(err) };
+            }
+
+            // Check if PRD was just saved
+            const stored = prdStore.get(ctx.workspaceRoot);
+            if (stored && !prdContent) {
+                prdContent = stored;
+                session.prdContent = stored;
+                prdStore.delete(ctx.workspaceRoot); // consume it
+            }
+
+            session.history.push({
+                role: 'tool',
+                tool_call_id: tc.id,
+                name: tc.function.name,
+                content: typeof result === 'string' ? result : JSON.stringify(result)
+            });
+        }
+    }
+
+    return {
+        reply: finalReply,
+        sessionId,
+        history: session.history
+            .filter(m => m.role !== 'assistant' || m.content || m.tool_calls?.length)
+            .slice(-60),
+        prdContent,
+        model: llm.modelId
+    };
+}