feat: add dynamic tool loading system with Railway executor

Implements a complete dynamic tool loading system that allows the playground to discover and load tools from the TPMJS registry at runtime.

**Architecture:**
- Search tool package (@tpmjs/search-registry) - Searches registry for tools
- Search API endpoint (/api/tools/search) - Text-based search with scoring
- Pre-flight tool loading - Automatically searches and loads tools on every message
- Railway executor service (Deno) - Loads tools from esm.sh via HTTP imports
- Dynamic tool loader - Calls Railway to load and execute tools remotely

**Key Components:**

1. Railway Executor (apps/railway-executor/)
   - Deno-based service that natively supports HTTP imports
   - Endpoints: /load-and-describe, /execute-tool, /cache/stats, /cache/clear
   - Deploys to Railway with deno run --allow-net --allow-env server.ts

2. Search Tool Package (packages/tools/search-registry/)
   - AI SDK v6 tool for searching TPMJS registry
   - Uses jsonSchema + inputSchema pattern
   - Searches /api/tools/search endpoint

3. Search API (apps/web/src/app/api/tools/search/)
   - Text-based search with composite scoring
   - Scores: text relevance + quality boost + download boost
   - Returns tool metadata with importUrl for dynamic loading

4. Dynamic Tool Loader (apps/playground/src/lib/dynamic-tool-loader.ts)
   - Calls Railway service to load tools from esm.sh
   - Creates tool wrappers that execute remotely
   - Process-level module cache + per-conversation tracking

5. Pre-flight Loading (apps/playground/src/app/api/chat/route.ts)
   - Automatically searches for tools on every user message
   - Loads top 5 matching tools before agent processes request
   - Merges with static tools for seamless experience

**Technical Decisions:**
- Deno over Node.js: Native HTTP import support without flags
- Remote execution: Tools run in Railway sandbox, not Vercel
- Pre-flight loading: Better UX than two-turn search pattern
- Text search: BM25 had dependency issues, simple scoring works well

**Environment Variables:**
- RAILWAY_SERVICE_URL: https://endearing-commitment-production.up.railway.app

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

apps/web/src/app/api/tools/search/route.ts

@@ -0,0 +1,124 @@
+import { prisma } from '@tpmjs/db';
+import { NextResponse } from 'next/server';
+
+export const runtime = 'nodejs';
+export const dynamic = 'force-dynamic';
+export const maxDuration = 60;
+
+// Simple text-based search scoring (fallback until BM25 is fixed)
+function calculateTextScore(query: string, document: string): number {
+  const queryTokens = query.toLowerCase().split(/\s+/);
+  const docLower = document.toLowerCase();
+
+  let score = 0;
+
+  for (const token of queryTokens) {
+    // Exact match in document
+    if (docLower.includes(token)) {
+      score += 1;
+    }
+
+    // Boost if token appears in beginning (likely more relevant)
+    if (docLower.startsWith(token)) {
+      score += 0.5;
+    }
+  }
+
+  return score;
+}
+
+export async function GET(request: Request) {
+  console.log('🔎 [SEARCH API] Request received');
+
+  try {
+    const { searchParams } = new URL(request.url);
+    const query = searchParams.get('q') || '';
+    const category = searchParams.get('category');
+    const limit = Math.min(Number.parseInt(searchParams.get('limit') || '10'), 50);
+
+    console.log(`🔎 [SEARCH API] Query: "${query}", Category: ${category}, Limit: ${limit}`);
+
+    // Fetch all tools with package info
+    const tools = await prisma.tool.findMany({
+      include: { package: true },
+      where: category
+        ? {
+            package: { category },
+          }
+        : undefined,
+    });
+
+    console.log(`📊 [SEARCH API] Found ${tools.length} tools in database`);
+
+    // Build searchable documents and calculate scores
+    const scoredResults = tools.map((tool) => {
+      const document = [
+        tool.description,
+        tool.exportName,
+        tool.package.npmPackageName,
+        tool.package.npmDescription || '',
+        ...(tool.package.npmKeywords || []),
+      ].join(' ');
+
+      const textScore = calculateTextScore(query, document);
+      const qualityBoost = Number.parseFloat(tool.qualityScore || '0') * 0.5;
+      const downloadBoost = Math.log10((tool.package.npmDownloadsLastMonth || 0) + 1) * 0.1;
+      const finalScore = textScore + qualityBoost + downloadBoost;
+
+      return { tool, score: finalScore };
+    });
+
+    // Sort by score and take top N
+    const topResults = scoredResults
+      .filter(({ score }) => score > 0) // Only include results with matches
+      .sort((a, b) => b.score - a.score)
+      .slice(0, limit + 1);
+
+    const hasMore = topResults.length > limit;
+    const results = hasMore ? topResults.slice(0, limit) : topResults;
+
+    console.log(`✅ [SEARCH API] Returning ${results.length} results (hasMore: ${hasMore})`);
+
+    // Format response to match existing /api/tools structure
+    return NextResponse.json({
+      success: true,
+      query,
+      filters: { category },
+      results: {
+        total: scoredResults.filter(({ score }) => score > 0).length,
+        returned: results.length,
+        tools: results.map(({ tool }) => ({
+          id: tool.id,
+          exportName: tool.exportName,
+          description: tool.description,
+          qualityScore: tool.qualityScore,
+          package: {
+            npmPackageName: tool.package.npmPackageName,
+            npmVersion: tool.package.npmVersion,
+            category: tool.package.category,
+            frameworks: tool.package.frameworks,
+            env: tool.package.env,
+            npmRepository: tool.package.npmRepository,
+            isOfficial: tool.package.isOfficial,
+            npmDownloadsLastMonth: tool.package.npmDownloadsLastMonth,
+          },
+          importUrl: `https://esm.sh/${tool.package.npmPackageName}@${tool.package.npmVersion}`,
+          cdnUrl: `https://cdn.jsdelivr.net/npm/${tool.package.npmPackageName}@${tool.package.npmVersion}/+esm`,
+        })),
+      },
+      pagination: {
+        limit,
+        hasMore,
+      },
+    });
+  } catch (error) {
+    console.error('❌ [SEARCH API] Error:', error);
+    return NextResponse.json(
+      {
+        success: false,
+        error: error instanceof Error ? error.message : 'Search failed',
+      },
+      { status: 500 }
+    );
+  }
+}