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/inject.go

@@ -0,0 +1,79 @@
+package rag
+
+import (
+	"fmt"
+	"strings"
+)
+
+func BuildContextBlock(results []SearchResult, maxTokens int) string {
+	if len(results) == 0 {
+		return ""
+	}
+	if maxTokens <= 0 {
+		maxTokens = 4000
+	}
+	maxChars := maxTokens * 4
+
+	var b strings.Builder
+	b.WriteString("<rag_context>\n")
+	b.WriteString("The following context was retrieved from indexed documents to help answer the user's question.\n\n")
+
+	for i, r := range results {
+		entry := fmt.Sprintf("--- Source: %s (relevance: %.2f) ---\n%s\n\n", r.DocumentName, r.Score, r.Content)
+		if b.Len()+len(entry) > maxChars {
+			break
+		}
+		b.WriteString(entry)
+		_ = i
+	}
+
+	b.WriteString("</rag_context>\n")
+	return b.String()
+}
+
+func ExtractRAGQueries(message string) (queries []string, cleaned string) {
+	cleaned = message
+	parts := strings.Split(message, "#")
+	if len(parts) <= 1 {
+		return nil, message
+	}
+
+	var queryParts []string
+	var textParts []string
+
+	for i, part := range parts {
+		if i == 0 {
+			textParts = append(textParts, part)
+			continue
+		}
+		part = strings.TrimSpace(part)
+		if part == "" {
+			continue
+		}
+
+		firstSpace := strings.IndexByte(part, ' ')
+		newline := strings.IndexByte(part, '\n')
+
+		end := len(part)
+		if firstSpace > 0 && (newline < 0 || firstSpace < newline) {
+			end = firstSpace
+		} else if newline > 0 {
+			end = newline
+		}
+
+		query := strings.TrimSpace(part[:end])
+		if query != "" {
+			queryParts = append(queryParts, query)
+		}
+		if end < len(part) {
+			textParts = append(textParts, part[end:])
+		}
+	}
+
+	if len(queryParts) > 0 {
+		cleaned = strings.Join(textParts, " ")
+		cleaned = strings.TrimSpace(cleaned)
+	}
+
+	return queryParts, cleaned
+}