feat(KB-620): complete Step 7 — Migration and first-run experience

- Add fn init command for initializing new kb projects
- Add auto-migration check at CLI startup
- Add /api/setup-state and /api/complete-setup dashboard endpoints
- Add SetupState and CompleteSetupInput types to dashboard API
- Add migration and rollback documentation to AGENTS.md
- Create changeset for multi-project migration feature

replace_kb.py

@@ -0,0 +1,61 @@
+import os
+import re
+
+ROOT = '/Users/eclipxe/Projects/kb'
+
+# No longer skipping .kb — process everything except git, node_modules, dist, backups
+SKIP_DIRS = {'.git', 'node_modules', 'dist', '.fusion-backup-20260331-223358'}
+SKIP_FILES = {'replace_kb.py', 'replace_kb.py.bak'}
+
+changed = []
+errors = []
+
+for dirpath, dirnames, filenames in os.walk(ROOT):
+    # Prune directories in-place
+    dirnames[:] = [d for d in dirnames if d not in SKIP_DIRS]
+
+    for filename in filenames:
+        if filename in SKIP_FILES:
+            continue
+        full_path = os.path.join(dirpath, filename)
+        rel_path = os.path.relpath(full_path, ROOT)
+
+        try:
+            with open(full_path, 'rb') as fh:
+                raw = fh.read()
+        except Exception as e:
+            errors.append(f"READ {rel_path}: {e}")
+            continue
+
+        # Skip binary files (check for null bytes)
+        if b'\x00' in raw:
+            continue
+
+        try:
+            content = raw.decode('utf-8')
+        except UnicodeDecodeError:
+            try:
+                content = raw.decode('latin-1')
+            except Exception as e:
+                errors.append(f"DECODE {rel_path}: {e}")
+                continue
+
+        new_content = content.replace('kb.db', 'fusion.db')
+        new_content = re.sub(r'\.kb(?![a-zA-Z0-9_\-])', '.fusion', new_content)
+
+        if new_content != content:
+            try:
+                with open(full_path, 'w', encoding='utf-8') as fh:
+                    fh.write(new_content)
+                changed.append(rel_path)
+            except Exception as e:
+                errors.append(f"WRITE {rel_path}: {e}")
+
+print(f"Changed {len(changed)} files:")
+for f in sorted(changed):
+    print(f"  {f}")
+
+if errors:
+    print(f"\nErrors ({len(errors)}):")
+    for e in errors:
+        print(f"  {e}")