docs: Remove 'Hotspots' subsystem doc.

We no longer have 'Hotspots' to introduce users
to important UI elements.

We now use one time banners for it.

docs/subsystems/hotspots.md

@@ -1,77 +0,0 @@
-# Hotspots
-
-Hotspots introduce users to important UI elements. They are an effective
-means of guiding users towards new features and providing context where
-Zulip's UI may not be self-evident.
-
-## Adding a new hotspot
-
-... is easy! If you are working on a new feature or think highlighting a
-certain UI element would improve Zulip's user experience, we welcome you to
-[open an issue](https://github.com/zulip/zulip/issues/new?title=hotspot%20request:)
-for discussion.
-
-### Step 1: Create hotspot content
-
-In `zerver/lib/hotspots.py`, add your content to the `ALL_HOTSPOTS` dictionary.
-Each key-value pair in `ALL_HOTSPOTS` associates the name of the hotspot with the
-content displayed to the user.
-
-```python
-ALL_HOTSPOTS = {
-    ...
-    'new_hotspot_name': {
-        'title': 'Provide a concise title',
-        'description': 'A helpful explanation goes here.',
-    },
-}
-```
-
-### Step 2: Configure hotspot placement
-
-The target element and visual orientation of each hotspot is specified in
-`HOTSPOT_LOCATIONS` of `web/src/hotspots.ts`.
-
-The `icon_offset` property specifies where the pulsing icon is placed _relative to
-the width and height of the target element_.
-
-By default, `popovers.compute_placement` is used to responsively
-determine whether a popover is best displayed above (TOP), below (BOTTOM),
-on the left (LEFT), on the right (RIGHT), or if none of those options fit,
-directly in the center of the message viewport (VIEWPORT_CENTER).
-
-However, if you would like to fix the orientation of a hotspot popover, a
-`popover` property can be additionally specified.
-
-### Step 3: Test manually
-
-To test your hotspot in the development environment, set
-`ALWAYS_SEND_ALL_HOTSPOTS = True` in `zproject/dev_settings.py`, and
-invoke `hotspots.initialize()` in your browser console. Every hotspot
-should be displayed.
-
-Here are some visual characteristics to confirm:
-
-- popover content is readable
-- icons reposition themselves on resize
-- icons are hidden and shown along with their associated elements
-- popovers reposition and reorient themselves on resize
-
-### Step 4 (if necessary): Tweak hotspot icon z-index
-
-Hotspot icons are assigned a [z-index](https://developer.mozilla.org/en-US/docs/Web/CSS/z-index)
-of 100 by default, which positions them in front of all message viewport
-content and behind sidebars and overlays. If a hotspot is associated with
-a target element on a sidebar or overlay, the icon's z-index may need to
-be increased to 101, 102, or 103.
-
-This adjustment can be made at the bottom of `web/styles/hotspots.css`:
-
-```css
-#hotspot_new_hotspot_name_icon {
-    z-index: 103;
-}
-```
-
-Hotspot popover overlays are assigned the highest z-index within the web app
-of 104, so icon z-indexing should not be greater than 103.

docs/subsystems/index.md

@@ -22,7 +22,6 @@ management-commands
 schema-migrations
 hashchange-system
 emoji
-hotspots
 full-text-search
 email
 analytics

tools/linter_lib/custom_check.py

@@ -106,9 +106,6 @@ markdown_whitespace_rules: List["Rule"] = [
     {
         "pattern": "^#+[A-Za-z0-9]",
         "description": "Missing space after # in heading",
-        "exclude_line": {
-            ("docs/subsystems/hotspots.md", "#hotspot_new_hotspot_name_icon {"),
-        },
         "good_lines": ["### some heading", "# another heading"],
         "bad_lines": ["###some heading", "#another heading"],
     },

zerver/lib/onboarding_steps.py

@@ -1,5 +1,3 @@
-# See https://zulip.readthedocs.io/en/latest/subsystems/hotspots.html
-# for documentation on this subsystem.
 from dataclasses import dataclass
 from typing import Any, Dict, List