keys: Improve descriptions of hotkeys that switch narrows.

- Use "zoom in/out" to simplify and shorten the longest description,
while also being clear on the choice of key being 'z'
- Consistently use "Go to" instead of "Narrow" for the menu buttons
- Introduce the usage of "feed" (combined feed & direct message feed)
- Switch to using "your" instead of "all".

Hotkeys document regenerated.

Author: Niloth-p

Diff for: docs/hotkeys.md

@@ -34,11 +34,11 @@
 |Narrow to the stream of the current message|<kbd>s</kbd>|
 |Narrow to the topic of the current message|<kbd>S</kbd>|
 |Narrow to compose box message recipient|<kbd>Meta</kbd> + <kbd>.</kbd>|
-|Narrow to a topic/direct-chat, or stream/all-direct-messages|<kbd>z</kbd>|
-|Narrow to all messages|<kbd>a</kbd> / <kbd>Esc</kbd>|
-|Narrow to all direct messages|<kbd>P</kbd>|
-|Narrow to all starred messages|<kbd>f</kbd>|
-|Narrow to messages in which you're mentioned|<kbd>#</kbd>|
+|Zoom in/out the message's conversation context|<kbd>z</kbd>|
+|Go to your combined feed|<kbd>a</kbd> / <kbd>Esc</kbd>|
+|Go to your direct message feed|<kbd>P</kbd>|
+|Go to your starred messages|<kbd>f</kbd>|
+|Go to messages in which you're mentioned|<kbd>#</kbd>|
 
 ## Searching
 |Command|Key Combination|

Diff for: zulipterminal/config/keys.py

@@ -175,7 +175,7 @@ class KeyBinding(TypedDict):
     'TOGGLE_NARROW': {
         'keys': ['z'],
         'help_text':
-            'Narrow to a topic/direct-chat, or stream/all-direct-messages',
+            "Zoom in/out the message's conversation context",
         'key_category': 'narrow',
     },
     'REACTION_AGREEMENT': {
@@ -190,22 +190,22 @@ class KeyBinding(TypedDict):
     },
     'ALL_MESSAGES': {
         'keys': ['a', 'esc'],
-        'help_text': 'Narrow to all messages',
+        'help_text': 'Go to your combined feed',
         'key_category': 'narrow',
     },
     'ALL_PM': {
         'keys': ['P'],
-        'help_text': 'Narrow to all direct messages',
+        'help_text': 'Go to your direct message feed',
         'key_category': 'narrow',
     },
     'ALL_STARRED': {
         'keys': ['f'],
-        'help_text': 'Narrow to all starred messages',
+        'help_text': 'Go to your starred messages',
         'key_category': 'narrow',
     },
     'ALL_MENTIONS': {
         'keys': ['#'],
-        'help_text': "Narrow to messages in which you're mentioned",
+        'help_text': "Go to messages in which you're mentioned",
         'key_category': 'narrow',
     },
     'NEXT_UNREAD_TOPIC': {