chore: v2.8.15 — Oh My Pi login sharing, omp --allow-home, Markdown Preview default, first-login password

- omp-share.js: an admin's switch (S3) runs omp's own auth broker + gateway as
  the host on loopback; a member's omp pane reaches it as a scoped client keyed
  by its pane token (clients file = live omp panes only), runs on
  --model agenthub/<model>, never holds a credential.
- omp catalog: --allow-home, so a workspace at the account's home keeps its
  sessions there (they were recorded under a temp dir and dropped).
- Settings → Appearance → Open Markdown as: Preview (default) or Raw, for
  Files/Changes, the config viewer and a chat's file panel.
- First-login password change and password rules, avatar URLs, Artifacts
  "Mine" includes installed shared skills/plugins, a member's own hook pages.

client/src/i18n/locales/en/common.json

@@ -198,7 +198,15 @@
     "tooMany": "Too many failed attempts — try again in a few minutes",
     "logout": "Sign out",
     "noAccount": "No account yet? Ask your administrator to create one.",
-    "signedInAs": "Signed in as {{name}} ({{role}})"
+    "signedInAs": "Signed in as {{name}} ({{role}})",
+    "mustChangeTitle": "Choose your own password",
+    "mustChangeSubtitle": "Your administrator gave you a starting password. Choose your own before you continue.",
+    "currentPassword": "Current password",
+    "newPassword": "New password",
+    "confirmPassword": "Confirm new password",
+    "mismatch": "The two new passwords differ",
+    "mustChangeSubmit": "Save and continue",
+    "saving": "Saving…"
   },
   "insights": {
     "help": {