Initial commit: pi-project-map skill scaffolding

- Design doc with full spec (dense markdown format, hybrid AST+LLM pipeline,
  consumption model, stale data mitigation)
- Implementation plan with 6 milestones and rollout strategy
- TypeScript package structure with all source stubs
- CLI entry point, formatter, discover, init, patch, validate, extract, merge
- Pi SKILL.md with tool definitions and format documentation

src/discover.ts

@@ -0,0 +1,56 @@
+import { readdirSync, statSync } from 'fs';
+import { join, relative } from 'path';
+import ignore from 'ignore';
+
+const DEFAULT_IGNORE = [
+  'node_modules', '.git', 'dist', 'build', 'coverage',
+  '.next', '.venv', '__pycache__', '.DS_Store', '*.log'
+];
+
+export interface DirectoryEntry {
+  dirPath: string;
+  relativePath: string;
+  files: string[];
+}
+
+export function discoverProject(rootPath: string): DirectoryEntry[] {
+  const ig = ignore().add(DEFAULT_IGNORE);
+  const gitignorePath = join(rootPath, '.gitignore');
+  try {
+    const gitignoreContent = require('fs').readFileSync(gitignorePath, 'utf8');
+    ig.add(gitignoreContent);
+  } catch { /* no .gitignore */ }
+
+  const entries: DirectoryEntry[] = [];
+
+  function walk(dir: string) {
+    const relDir = relative(rootPath, dir) || '.';
+    if (ig.ignores(relDir)) return;
+
+    const items = readdirSync(dir);
+    const files: string[] = [];
+    const subdirs: string[] = [];
+
+    for (const item of items) {
+      const relPath = join(relDir, item);
+      if (ig.ignores(relPath)) continue;
+
+      const fullPath = join(dir, item);
+      const st = statSync(fullPath);
+      if (st.isDirectory()) {
+        subdirs.push(fullPath);
+      } else {
+        files.push(item);
+      }
+    }
+
+    entries.push({ dirPath: dir, relativePath: relDir, files });
+
+    for (const subdir of subdirs) {
+      walk(subdir);
+    }
+  }
+
+  walk(rootPath);
+  return entries;
+}