feat: add defaultModel to plugin manifests

Add defaultModel: sonnet to all plugin manifests that have agents,
establishing the plugin-level default in the model inheritance chain.

Version bumps:
- projman: 3.2.0 → 3.3.0 (minor: new feature)
- pr-review: 1.0.0 → 1.1.0 (minor: new feature)
- data-platform: 1.0.0 → 1.1.0 (minor: new feature)
- viz-platform: 1.0.0 → 1.1.0 (minor: new feature)
- code-sentinel: 1.0.0 → 1.0.1 (patch: config addition)
- contract-validator: 1.0.0 → 1.1.0 (minor: new feature)

Fixes #305

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

plugins/pr-review/.claude-plugin/plugin.json

@@ -1,6 +1,7 @@
 {
   "name": "pr-review",
-  "version": "1.0.0",
+  "version": "1.1.0",
+  "defaultModel": "sonnet",
   "description": "Multi-agent pull request review with confidence scoring and actionable feedback",
   "author": {
     "name": "Leo Miranda",