fix(mosaic): resolve framework scripts via import.meta.url

Previously, resolveTool() used createRequire + req.resolve('@mosaic/mosaic/package.json')
to locate the bundled framework directory. The published package.json only exports the
root '.' subpath, so Node throws ERR_PACKAGE_PATH_NOT_EXPORTED for './package.json'. The
catch block silently swallowed this error and fell through to the MOSAIC_HOME fallback
path (~/.config/mosaic/tools/_scripts/mosaic-doctor), which does not exist on a user's
machine, causing every framework-delegated subcommand (doctor, coord, etc.) to fail with
'[mosaic] Script not found'.

Two-layer fix:
1. Replace the createRequire approach with import.meta.url-based resolution. The built
   file lives at dist/commands/launch.js, so ../../framework/tools/... always resolves to
   the bundled framework directory regardless of how the package exports field is
   configured. This is layout-stable for both the published package and local dev.
2. Add './package.json' and './framework/*' subpath exports to package.json as belt-and-
   suspenders, keeping subpath access working for any future caller.

Bump version to 0.0.18.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/mosaic/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@mosaic/mosaic",
-  "version": "0.0.17",
+  "version": "0.0.18",
   "repository": {
     "type": "git",
     "url": "https://git.mosaicstack.dev/mosaic/mosaic-stack.git",
@@ -18,7 +18,9 @@
     ".": {
       "types": "./dist/index.d.ts",
       "default": "./dist/index.js"
-    }
+    },
+    "./package.json": "./package.json",
+    "./framework/*": "./framework/*"
   },
   "scripts": {
     "build": "tsc",