chore(v0.18.2.fork.1): bump version to 0.18.2-fork.1

Aligns package.json + VERSION file so `gbrain --version` reflects fork
identity. Format: SemVer pre-release segment '-fork.1' (NOT build
metadata '+fork.1' — many tools treat '+' as build metadata to be
stripped, while pre-release tags are first-class for sort/compare).

Verified: bun run src/cli.ts --version → "gbrain 0.18.2-fork.1"

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

VERSION

@@ -1 +1 @@
-0.18.2
+0.18.2-fork.1

package.json

@@ -1,6 +1,6 @@
 {
   "name": "gbrain",
-  "version": "0.18.2",
+  "version": "0.18.2-fork.1",
   "description": "Postgres-native personal knowledge brain with hybrid RAG search",
   "type": "module",
   "main": "src/core/index.ts",