Extensions: hub bridge for tasks, contacts and calendar (asked of the person once), Sites in My Store, and four example extensions

- hub.tasks / hub.contacts / hub.calendar in the extension sandbox; each kind of access is approved by the person and remembered per extension
- My Store: Sites kind (any web link, optionally shown inside the hub)
- Examples: notes and checklists, habit tracker, kitchen converter and scaler, weather and verse of the day

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

README.md

@@ -159,7 +159,8 @@ One **Store** tab (turn it on per person) with sections for **Books** (the free
 - **Books** (EPUB, PDF, MOBI, AZW3, DOCX): *Add to my library* puts a copy on that person's shelf, or download it.
 - **Music** (MP3, M4A, AAC, FLAC, OGG, OPUS, WAV): an album can have many tracks; they play in the hub's player and can be downloaded.
 - **Apps**: any files to download (an APK, an installer...), with an optional link and version. The hub does not run them.
-- **Extensions**: one self-contained `.html` file that adds a feature to the hub. A person installs it from My Store and it opens inside the Store. It runs in a sandbox with no access to the hub's sign-in or data (and `connect-src https:` only), and talks to the hub through a small `hub` object: `hub.storage.get/set/all/remove` (its own settings for that person, up to 256 KB), `hub.user()` (the person's name), `hub.toast(text)` and `hub.open(url)`. See `docs/extensions/notepad.html` for a complete example.
+- **Sites**: any website as a card. It opens in a new tab, or inside the hub if you tick *Open inside the hub* (some sites refuse to be shown that way).
+- **Extensions**: one self-contained `.html` file that adds a feature to the hub. A person installs it from My Store and it opens inside the Store. It runs in a sandbox with no access to the hub's sign-in or data (and `connect-src https:` only), and talks to the hub through a small `hub` object: `hub.storage.get/set/all/remove` (its own settings for that person, up to 256 KB), `hub.user()` (the person's name), `hub.toast(text)` and `hub.open(url)`. It can also ask for hub data, which the person approves the first time (and which is forgotten when the extension is removed): `hub.tasks.lists() / list(listId) / add({ title, notes, due, list }) / complete(listId, taskId)`, `hub.contacts.list() / add({ name, email, phone, org })` and `hub.calendar.events(from, to) / add({ title, start, end, allDay })` (dates as `YYYY-MM-DD`, times as `YYYY-MM-DDTHH:MM`). A refused request rejects with an error. Ready-made examples are in `docs/extensions/`: **notes.html** (notes and checklists, can send items to Tasks), **tracker.html** (habit and Bible-reading streaks), **kitchen.html** (unit converter and recipe scaler that can add to your Shopping list), **weather.html** (forecast plus a verse of the day) and **notepad.html** (the smallest one).
 
 Files are kept in the data folder under `mystore/` (up to 1 GB each; extensions up to 2 MB). Only an admin can add, change or delete items.