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.

docs/LANES.md

@@ -636,6 +636,10 @@ reads the workspace's git surface in five modes:
   A workspace folder that is **not a git repo** still gets the tree and
   quick-open, read off the disk (no colours; `.git` hidden, `node_modules`
   listed but never entered, symlinks never followed, at most 20 000 entries).
+  A whole `.md` file opens rendered, with a **Raw**/**Preview** button for
+  that file; Settings → Appearance → **Open Markdown as** (`agenthub.markdown.view`,
+  `client/src/lib/markdownView.ts`, synced to the account) makes Raw the
+  default instead — here, in the config file viewer and in a chat's file panel.
   **Download** on a file's right-click menu, or in an open file's header,
   saves that file (`/git/download`, any type, up to 512 MB); the **Upload**
   button beside the finder uploads files to the workspace root and **Upload