docs(user): rewrite collections to the screenshot-free standard

The old page was stale in ways the standard now forbids: spatial
language ("top-right"), documented URL query params users should never
need, no mention of smart collections or podcast episodes, no hand-off
to the filter docs.

Ground-truthed against the templates: Static vs lightning-Smart type
choice, Books/Podcast episodes rules scope, Add Items picker ( Books /
Episodes tabs, Add Selected, Remove Selected), Edit Rules -> Filter
tree -> Apply to Collection, Play as Sequence with the listening-order
picker (Feed order / reversed / oldest / newest), Hide finished books
(reading-queue mode) and Show Up Next strip toggles, system shelves
(Continue Reading, Recently Added, Recently Read, Not Started, Continue
Series) and Restore System -> Restore.

Plain language per the user-docs tone contract: short sentences,
pattern-first (one shelf concept, four flavors), every step ends in an
outcome, rules taught by LINK to the filter guide (reference, never
restate). Every quoted control exists as a literal and is glossaried in
ui-controls.md (gate-checked).

docs/user/collections.md

@@ -1,42 +1,118 @@
 # Collections
 
-Collections allow you to organize books across multiple libraries.
+A collection is a personal shelf you name yourself. You put your books and
+podcast episodes on it, and it appears as a section on your dashboard.
 
-## Viewing Collections
+That is the whole idea. Everything below is variations on it.
 
-### From Collections Page
+## The one pattern, four flavors
 
-Navigate to **Collections** (sidebar navigation) to see all your collections. Clicking on a collection shows ALL books in that collection across all libraries.
+Every collection behaves the same way on the outside: it has a name, an icon,
+a color, and a list of items. The flavors differ in how items *join*:
 
-### From Dashboard
+| Flavor | How items join | Right for |
+| --- | --- | --- |
+| **Static** | You pick each item by hand | Curated lists — "books for the trip", "new house ideas" |
+| **⚡ Smart** (books) | Rules match books live, forever | "everything by Asimov", "still not started", "over 400 pages" |
+| **⚡ Smart** (podcast episodes) | Rules match episodes live — and they can play back-to-back | "catch up on my feeds", "episodes to finish" |
+| **System** (built-in) | Bookhoard maintains them | Continue Reading, Recently Added, Recently Read, Not Started, Continue Series |
 
-When viewing a specific library's dashboard, collections only show books from that library. Clicking "View All" preserves this context and shows only books from that library in the collection.
+A collection holds **books and podcast episodes** — mix them if you like.
 
-### Library Filtering
+The **⚡ Smart** badge means the same thing everywhere it appears: *membership
+is matched by rules right now — always current, nothing to refresh*.
 
-- **No filter** (`/collections/favorites`): Shows all books across all libraries
-- **With filter** (`/collections/favorites?library_id=xxx`): Shows only books from the specified library
+## Creating a collection
 
-## Creating Collections
+1. Open the **Collections** page (sidebar navigation)
+2. Click **New Collection**
+3. Choose the **Type**:
+   - **Static** — pick items by hand
+   - **⚡ Smart** — match by rules, always live
+4. If you picked **⚡ Smart**, choose the **Rules scope**: **📚 Books** or
+   **🎧 Podcast episodes**
+5. Fill in the rest: **Name**, **Description**, an **Icon** you can search or
+   pick, and a **Color**
+6. Click **Create Collection**
 
-1. Go to **Collections** (sidebar navigation)
-2. Click **New Collection** (top-right) — or **Create Your First Collection** if the list is empty
-3. Fill in the details:
-   - **Name** - Collection name
-   - **Description** - Optional description
-   - **Icon** - Pick from the icon grid
-   - **Color** - Pick a color swatch
-4. Click **Create Collection**
+Starting from a completely empty account? The button **Create Your First
+Collection** does the same thing.
 
-## Managing Collections
+## Adding items by hand (Static collections)
 
-Each collection in the list has icon buttons on its card:
+1. Open the collection from the **Collections** page
+2. Click **Add Items**
+3. Pick the tab for what you want:
+   - **📚 Books** — searchable by the **Search books...** box, and the
+     **Author** and **Genre** boxes
+   - **🎧 Episodes** — the episodes of the feeds you subscribe to
+4. Click one or more items — a checkmark marks what you picked; the bottom
+   of the window counts them for you
+5. Click **Add Selected**
 
-- **Edit** - Opens the edit form to change name, description, icon, or color. Click **Update Collection** to save.
-- **Delete** - Removes the collection after a confirmation prompt.
+To take items out, check them on the collection page and click
+**Remove Selected** (it asks first).
 
-Deleted a system collection by mistake? The **Restore System** button on the Collections page brings back system collections.
+While checking what is in the collection, the **Search within collection...**
+box narrows the view — it never removes anything.
 
-### Dashboard Sections
+## Rules (how ⚡ Smart collections work)
 
-Collections appear as sections on your dashboard. Show, hide, and reorder them from the dashboard's **Customize Dashboard** settings (see [Dashboard](dashboard.md)).
+A smart collection keeps its own list of rules, the same rules that power the
+filter drawer. On the collection's page, click **Edit Rules** to open the
+rules editor: build your groups and rules in the **Filter tree**, then click
+**Apply to Collection**. From that point the collection matches those rules
+by itself — add a book that matches and it appears without you doing
+anything.
+
+Rules live in one guide, so this page does not repeat them. The full how-to
+walks through groups, ALL/ANY, and value picking in
+[Filters — the complete guide](filters/index.md), ready-made examples are in
+the [cookbook](filters/cookbook.md), and
+[every filter field](filters/fields.md) lists what you can ask about.
+
+*Finding it again later:* open any collection's page and look for the
+**Edit Rules** button; the **⚡ Smart** badge in the page title marks a
+collection that is already matching.
+
+## Playing an episode collection
+
+When a collection holds a downloaded episode, it grows a **Play as Sequence**
+button: the episodes play one after another. Next to it, the order picker
+decides the sequence — **Feed order**, **Feed order (reversed)**,
+**Oldest first (pub date)**, or **Newest first (pub date)**. Your choice is
+remembered on the collection.
+
+## Changing a collection
+
+The pencil button on a collection card, or the edit control on the
+collection page, opens the edit form:
+
+- Change the **Name**, **Description**, **Icon**, **Color**
+- **Hide finished books (reading-queue mode)** — finished books drop off
+  this shelf, which keeps a to-read list short
+- **Show Up Next strip** — show the collection's Up Next strip where it is
+  used
+
+Click **Update Collection** to save. Deleting a collection asks first, and
+deleting only removes the shelf — never the books or episodes inside it.
+
+## System collections
+
+The five built-in shelves — **Continue Reading**, **Recently Added**,
+**Recently Read**, **Not Started**, **Continue Series** — work like any
+collection on the outside, but Bookhoard decides their membership by what
+happens while you read. They appear on your dashboard automatically.
+
+Deleted one and want it back? Click **Restore System** on the **Collections**
+page, pick the shelf from the list, and click **Restore**.
+
+## Your dashboard shelves
+
+Collections appear as sections on your dashboard, and you choose which ones
+show and in what order from the dashboard's own settings. That page's
+details live in [Dashboard](dashboard.md).
+
+*Finding your way back:* **Collections** is the sidebar page whose top has
+the only **New Collection** button — from a dashboard shelf's **View All**,
+the collection detail page is the place with **Add Items**.