feat: RAG, memory, plugins, lessons, file editor, split panes, Markdown rendering, PWA + UI overhaul

Major additions:
- RAG pipeline (indexing, chunking, search) with sidebar upload button
- Memory system with CRUD API
- Plugins and lessons modules
- MCP discovery and MCP server
- Advanced skills (auto-create, conditional, improver)
- Agent browser/image support, delegate, sessions
- File editor with CodeMirror in split panes
- Markdown rendering via react-markdown + KaTeX + highlight.js
- Raw markdown toggle
- PWA manifest + service worker
- Extension UI redesign with new design tokens and studio-style chat
- Pipeline API for chat streaming
- Mobile responsive layout

💘 Generated with Crush

Assisted-by: GLM-5.1 via Crush <crush@charm.land>

internal/rag/embed.go

@@ -0,0 +1,113 @@
+package rag
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"strings"
+	"time"
+)
+
+type EmbeddingClient struct {
+	apiKey  string
+	baseURL string
+	client  *http.Client
+}
+
+func NewEmbeddingClient(apiKey, baseURL string) *EmbeddingClient {
+	if baseURL == "" {
+		baseURL = "https://api.openai.com/v1"
+	}
+	return &EmbeddingClient{
+		apiKey:  apiKey,
+		baseURL: strings.TrimRight(baseURL, "/"),
+		client:  &http.Client{Timeout: 30 * time.Second},
+	}
+}
+
+type embeddingRequest struct {
+	Model string   `json:"model"`
+	Input []string `json:"input"`
+}
+
+type embeddingResponse struct {
+	Data []struct {
+		Embedding []float64 `json:"embedding"`
+		Index     int       `json:"index"`
+	} `json:"data"`
+	Usage struct {
+		TotalTokens int `json:"total_tokens"`
+	} `json:"usage"`
+}
+
+func (c *EmbeddingClient) Embed(texts []string, model string) ([][]float64, error) {
+	if len(texts) == 0 {
+		return nil, nil
+	}
+	if model == "" {
+		model = "text-embedding-3-small"
+	}
+
+	body := embeddingRequest{
+		Model: model,
+		Input: texts,
+	}
+
+	bodyBytes, err := json.Marshal(body)
+	if err != nil {
+		return nil, fmt.Errorf("marshal embedding request: %w", err)
+	}
+
+	url := c.baseURL + "/embeddings"
+	req, err := http.NewRequest("POST", url, bytes.NewReader(bodyBytes))
+	if err != nil {
+		return nil, fmt.Errorf("create embedding request: %w", err)
+	}
+
+	req.Header.Set("Content-Type", "application/json")
+	if c.apiKey != "" {
+		req.Header.Set("Authorization", "Bearer "+c.apiKey)
+	}
+
+	resp, err := c.client.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("send embedding request: %w", err)
+	}
+	defer resp.Body.Close()
+
+	respBody, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, fmt.Errorf("read embedding response: %w", err)
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("embedding API error (%d): %s", resp.StatusCode, string(respBody))
+	}
+
+	var embResp embeddingResponse
+	if err := json.Unmarshal(respBody, &embResp); err != nil {
+		return nil, fmt.Errorf("parse embedding response: %w", err)
+	}
+
+	result := make([][]float64, len(texts))
+	for _, data := range embResp.Data {
+		if data.Index < len(result) {
+			result[data.Index] = data.Embedding
+		}
+	}
+
+	return result, nil
+}
+
+func (c *EmbeddingClient) EmbedSingle(text, model string) ([]float64, error) {
+	results, err := c.Embed([]string{text}, model)
+	if err != nil {
+		return nil, err
+	}
+	if len(results) == 0 {
+		return nil, fmt.Errorf("no embedding returned")
+	}
+	return results[0], nil
+}