keys: Improve descriptions of hotkeys that switch narrows.

Replace "Narrow to":
- Use "View" instead of "Narrow to"
- Use "View all" for the narrow buttons
- Use "Open PM with" for the compose box message recipient

Rephrasing help texts:
- Use "zoom in/out" to simplify and shorten the longest description,
while also being clear on the choice of key being 'z'
- "messages in which you're mentioned" -> "messages you're mentioned in"
reduces length while retaining clarity

Hotkeys document regenerated.

docs/hotkeys.md

@@ -32,14 +32,14 @@
 ## Switching Messages View
 |Command|Key Combination|
 | :--- | :---: |
-|Narrow to the stream of the current message|<kbd>s</kbd>|
-|Narrow to the topic of the current message|<kbd>S</kbd>|
-|Narrow to a topic/direct-chat, or stream/all-direct-messages|<kbd>z</kbd>|
-|Narrow to compose box message recipient|<kbd>Meta</kbd> + <kbd>.</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>|
+|View the stream of the current message|<kbd>s</kbd>|
+|View the topic of the current message|<kbd>S</kbd>|
+|Zoom in/out the message's conversation context|<kbd>z</kbd>|
+|Open PM with compose box message recipient|<kbd>Meta</kbd> + <kbd>.</kbd>|
+|View all messages|<kbd>a</kbd> / <kbd>Esc</kbd>|
+|View all direct messages|<kbd>P</kbd>|
+|View all starred messages|<kbd>f</kbd>|
+|View all messages you're mentioned in|<kbd>#</kbd>|
 
 ## Searching
 |Command|Key Combination|

zulipterminal/config/keys.py

@@ -170,23 +170,23 @@ class KeyBinding(TypedDict):
     },
     'STREAM_NARROW': {
         'keys': ['s'],
-        'help_text': 'Narrow to the stream of the current message',
+        'help_text': 'View the stream of the current message',
         'key_category': 'narrowing',
     },
     'TOPIC_NARROW': {
         'keys': ['S'],
-        'help_text': 'Narrow to the topic of the current message',
+        'help_text': 'View the topic of the current message',
         'key_category': 'narrowing',
     },
     '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': 'narrowing',
     },
     'NARROW_MESSAGE_RECIPIENT': {
         'keys': ['meta .'],
-        'help_text': 'Narrow to compose box message recipient',
+        'help_text': 'Open PM with compose box message recipient',
         'key_category': 'narrowing',
     },
     'REACTION_AGREEMENT': {
@@ -201,22 +201,22 @@ class KeyBinding(TypedDict):
     },
     'ALL_MESSAGES': {
         'keys': ['a', 'esc'],
-        'help_text': 'Narrow to all messages',
+        'help_text': 'View all messages',
         'key_category': 'narrowing',
     },
     'ALL_PM': {
         'keys': ['P'],
-        'help_text': 'Narrow to all direct messages',
+        'help_text': 'View all direct messages',
         'key_category': 'narrowing',
     },
     'ALL_STARRED': {
         'keys': ['f'],
-        'help_text': 'Narrow to all starred messages',
+        'help_text': 'View all starred messages',
         'key_category': 'narrowing',
     },
     'ALL_MENTIONS': {
         'keys': ['#'],
-        'help_text': "Narrow to messages in which you're mentioned",
+        'help_text': "View all messages you're mentioned in",
         'key_category': 'narrowing',
     },
     'NEXT_UNREAD_TOPIC': {