feat(FN-2709): migrate Hermes runtime plugin to pi-ai streaming client

- Replace Hermes pi module integration with pi-ai session streaming and updated runtime adapter contracts
- Remove legacy engine guard scaffolding and add hermes-stream-client coverage for streaming behavior
- Rewrite plugin and engine e2e tests to align with the new runtime flow and regenerate dist artifacts
- Update Hermes runtime README and package metadata to document pi-ai execution expectations

plugins/fusion-plugin-hermes-runtime/dist/pi-module.js

@@ -1,13 +1,85 @@
-/**
- * Pi Module Seam
- *
- * Provides a mockable import path for pi functions used by the HermesRuntimeAdapter.
- * Tests intercept this module via `vi.mock("../pi-module.js", ...)`. The runtime
- * implementations come from @fusion/engine; the local types provide a loose
- * surface so the adapter doesn't have to depend on @fusion/engine's full types.
- */
-import { createFnAgent as _createFnAgent, promptWithFallback as _promptWithFallback, describeModel as _describeModel, } from "@fusion/engine";
-export const createFnAgent = _createFnAgent;
-export const promptWithFallback = _promptWithFallback;
-export const describeModel = _describeModel;
+import { randomUUID } from "node:crypto";
+import { getModel, streamSimple, } from "@mariozechner/pi-ai";
+const DEFAULT_PROVIDER = "anthropic";
+const DEFAULT_MODEL_ID = "claude-sonnet-4-5";
+function resolveStringSetting(value) {
+    return typeof value === "string" && value.trim().length > 0 ? value.trim() : undefined;
+}
+export function resolveModelConfig(settings) {
+    const provider = resolveStringSetting(settings?.provider) ?? resolveStringSetting(process.env.HERMES_PROVIDER) ?? DEFAULT_PROVIDER;
+    const modelId = resolveStringSetting(settings?.modelId) ?? resolveStringSetting(process.env.HERMES_MODEL_ID) ?? DEFAULT_MODEL_ID;
+    const apiKey = resolveStringSetting(settings?.apiKey) ?? resolveStringSetting(process.env.HERMES_API_KEY);
+    const thinkingLevel = resolveStringSetting(settings?.thinkingLevel) ?? resolveStringSetting(process.env.HERMES_THINKING_LEVEL) ?? undefined;
+    return { provider, modelId, apiKey, thinkingLevel };
+}
+export function createStreamSession(options) {
+    const model = getModel(options.provider, options.modelId);
+    return {
+        model,
+        systemPrompt: options.systemPrompt,
+        messages: [],
+        apiKey: options.apiKey,
+        thinkingLevel: options.thinkingLevel,
+        sessionId: randomUUID(),
+        lastModelDescription: `${model.provider}/${model.id}`,
+        callbacks: options.callbacks ?? {},
+        usage: undefined,
+        dispose: () => undefined,
+    };
+}
+export async function streamPrompt(session, _userMessage) {
+    const context = {
+        systemPrompt: session.systemPrompt,
+        messages: [...session.messages],
+    };
+    const options = {
+        sessionId: session.sessionId,
+    };
+    if (session.apiKey) {
+        options.apiKey = session.apiKey;
+    }
+    if (session.thinkingLevel) {
+        options.reasoning = session.thinkingLevel;
+    }
+    const stream = streamSimple(session.model, context, options);
+    let fullText = "";
+    for await (const event of stream) {
+        handleStreamEvent(event, session, (delta) => {
+            fullText += delta;
+        });
+    }
+    const finalMessage = await stream.result();
+    const responseText = finalMessage.content
+        .filter((content) => content.type === "text")
+        .map((content) => content.text)
+        .join("") || fullText;
+    session.messages.push({ role: "assistant", content: responseText });
+    session.lastModelDescription = `${session.model.provider}/${session.model.id}`;
+}
+function handleStreamEvent(event, session, onTextDelta) {
+    if (event.type === "text_delta") {
+        session.callbacks.onText?.(event.delta);
+        onTextDelta(event.delta);
+        return;
+    }
+    if (event.type === "thinking_delta") {
+        session.callbacks.onThinking?.(event.delta);
+        return;
+    }
+    if (event.type === "toolcall_end") {
+        session.callbacks.onToolStart?.(event.toolCall.name, event.toolCall.arguments);
+        session.callbacks.onToolEnd?.(event.toolCall.name, false, event.toolCall.arguments);
+        return;
+    }
+    if (event.type === "error") {
+        const errorMessage = event.error.errorMessage ?? "Hermes stream failed";
+        throw new Error(errorMessage);
+    }
+    if (event.type === "done") {
+        session.usage = event.message.usage;
+    }
+}
+export function describeStreamModel(session) {
+    return session.lastModelDescription;
+}
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