fix(manifest): restore stable version to 3.2.8, split beta into manifest-beta.json (#2428)

URGENT FIX. The prerelease agent's npm version run on PR #2427 left master's
manifest.json with version "3.2.9-beta.0", but Obsidian's community plugin
store reads manifest.json on master to determine which GitHub Release to
serve to new installers. With the stable release at 3.2.8 and master's
manifest pointing at a prerelease tag, plugin installs and updates were
breaking for users.

Fix:
- manifest.json on master: version back to "3.2.8" (the latest stable
  release). minAppVersion 1.7.2 and isDesktopOnly:false are preserved.
- manifest-beta.json (new): full manifest for 3.2.9-beta.0 so BRAT and
  similar beta-installer tools can locate the prerelease without us
  poisoning master's stable manifest.

The longer-term fix (version-bump.mjs + prerelease agent updates so
this can't recur) follows in a separate PR.

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

manifest-beta.json

@@ -0,0 +1,14 @@
+{
+  "id": "copilot",
+  "name": "Copilot",
+  "version": "3.2.9-beta.0",
+  "minAppVersion": "1.7.2",
+  "isDesktopOnly": false,
+  "description": "Your AI Copilot: Chat with Your Second Brain, Learn Faster, Work Smarter.",
+  "author": "Logan Yang",
+  "authorUrl": "https://twitter.com/logancyang",
+  "fundingUrl": {
+    "Buy Me a Coffee": "https://www.buymeacoffee.com/logancyang",
+    "GitHub Sponsor": "https://github.com/sponsors/logancyang"
+  }
+}

manifest.json

@@ -1,7 +1,7 @@
 {
   "id": "copilot",
   "name": "Copilot",
-  "version": "3.2.9-beta.0",
+  "version": "3.2.8",
   "minAppVersion": "1.7.2",
   "isDesktopOnly": false,
   "description": "Your AI Copilot: Chat with Your Second Brain, Learn Faster, Work Smarter.",