fix(release): move plugin-sdk's @fusion/core dep out of peerDependencies

The v1.0.0 release-bump misfire (0.4.1 + one minor changeset → 1.0.0
instead of 0.5.0) traced to changesets' assemble-release-plan logic:

  1. getDependencyVersionRanges resolves "workspace:*" to the *exact*
     current version (not a wildcard).
  2. shouldBumpMajor escalates a dependent's bump to "major" whenever
     it has a peerDependency on a package whose new version falls
     outside the resolved range AND the bump is non-patch.
  3. plugin-sdk listed "@fusion/core": "workspace:*" as a peer dep, so
     a minor on @fusion/core (triggered via the fixed group) escalated
     plugin-sdk to major; the fixed group then carried every package
     to 1.0.0.

Both packages are private:true workspace-only — the peer-dep semantic
had no runtime effect, only mis-shaped the changesets dependency graph.
Moving it to "dependencies" makes the determineDependents path fall
into the non-peer branch (caps at "patch", does not escalate), so the
fixed group bumps as intended (verified: 0.5.0 + minor → 0.6.0).

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

packages/plugin-sdk/package.json

@@ -28,7 +28,7 @@
     "typescript": "^5.7.0",
     "vitest": "^3.1.0"
   },
-  "peerDependencies": {
+  "dependencies": {
     "@fusion/core": "workspace:*"
   },
   "engines": {