feat(02-02): create SessionStart context injection hook

- Read session metadata from stdin
- Check for startup/resume source
- Read index.json and conventions.json from .planning/intel/
- Silent exit if no intel files present

hooks/intel-session.js

@@ -0,0 +1,110 @@
+#!/usr/bin/env node
+// Codebase Intelligence - SessionStart Context Injection Hook
+// Injects codebase summary into Claude's context at session start
+
+const fs = require('fs');
+const path = require('path');
+
+/**
+ * Generate concise codebase summary for context injection
+ * Target: < 500 tokens to minimize context usage
+ */
+function generateSummary(index, conventions) {
+  const lines = [];
+
+  // File count
+  const fileCount = Object.keys(index.files || {}).length;
+  if (fileCount === 0) return null;
+
+  lines.push(`Indexed files: ${fileCount}`);
+
+  // Naming conventions (if detected with confidence)
+  if (conventions.naming?.exports?.dominant) {
+    const n = conventions.naming.exports;
+    lines.push(`Export naming: ${n.dominant} (${n.percentage}%)`);
+  }
+
+  // Key directories (top 5)
+  const dirs = Object.entries(conventions.directories || {});
+  if (dirs.length > 0) {
+    lines.push('');
+    lines.push('Key directories:');
+    for (const [dir, info] of dirs.slice(0, 5)) {
+      lines.push(`  ${dir}: ${info.purpose} (${info.files} files)`);
+    }
+  }
+
+  // Suffix patterns (top 3)
+  const suffixes = Object.entries(conventions.suffixes || {});
+  if (suffixes.length > 0) {
+    lines.push('');
+    lines.push('File patterns:');
+    for (const [suffix, info] of suffixes.slice(0, 3)) {
+      lines.push(`  ${suffix}: ${info.purpose} (${info.count} files)`);
+    }
+  }
+
+  // Key exports overview (categorize if enough data)
+  const allExports = [];
+  for (const [filePath, fileData] of Object.entries(index.files || {})) {
+    for (const exp of fileData.exports || []) {
+      if (exp !== 'default') {
+        allExports.push(exp);
+      }
+    }
+  }
+
+  if (allExports.length > 0) {
+    lines.push('');
+    lines.push(`Total exports: ${allExports.length}`);
+    // List a few example exports if available
+    if (allExports.length <= 10) {
+      lines.push(`Exports: ${allExports.join(', ')}`);
+    }
+  }
+
+  return lines.join('\n');
+}
+
+// Read JSON from stdin (standard hook pattern)
+let input = '';
+process.stdin.setEncoding('utf8');
+process.stdin.on('data', chunk => input += chunk);
+process.stdin.on('end', () => {
+  try {
+    const data = JSON.parse(input);
+
+    // Only inject on startup or resume
+    if (!['startup', 'resume'].includes(data.source)) {
+      process.exit(0);
+    }
+
+    // Check for intel files
+    const intelDir = path.join(process.cwd(), '.planning', 'intel');
+    const indexPath = path.join(intelDir, 'index.json');
+
+    if (!fs.existsSync(indexPath)) {
+      process.exit(0);  // No intel, skip silently
+    }
+
+    // Read intel files
+    const index = JSON.parse(fs.readFileSync(indexPath, 'utf8'));
+
+    let conventions = { naming: {}, directories: {}, suffixes: {} };
+    const conventionsPath = path.join(intelDir, 'conventions.json');
+    if (fs.existsSync(conventionsPath)) {
+      conventions = JSON.parse(fs.readFileSync(conventionsPath, 'utf8'));
+    }
+
+    // Generate and output summary
+    const summary = generateSummary(index, conventions);
+    if (summary) {
+      process.stdout.write(`<codebase-intelligence>\n${summary}\n</codebase-intelligence>`);
+    }
+
+    process.exit(0);
+  } catch (error) {
+    // Silent failure - never block Claude
+    process.exit(0);
+  }
+});