CV2: Add missing limits for alt texts, ID clarifications (#7537)

* Add limits to alt texts

* Clarify pre-CV2 component IDs, 0 ->1 behavior

* Move pre-CV2 notes to "Legacy Message Component Behavior"

* Document sending 0 IDs in 'Anatomy of a Component'

Also Reworded legacy section

Author: freya022

docs/components/reference.mdx

@@ -64,7 +64,7 @@ All components have the following fields:
 | type  | integer | The [type](/docs/components/reference#component-object-component-types) of the component |
 | id?   | integer | 32 bit integer used as an optional identifier for component                              |
 
-The `id` field is optional and is used to identify components in the response from an interaction that aren't interactive components. The `id` must be unique within the message and is generated sequentially if left empty. Generation of `id`s won't use another `id` that exists in the message if you have one defined for another component.
+The `id` field is optional and is used to identify components in the response from an interaction. The `id` must be unique within the message and is generated sequentially if left empty. Generation of `id`s won't use another `id` that exists in the message if you have one defined for another component. Sending components with an `id` of `0` is allowed but will be treated as empty and replaced by the API.
 
 ###### Custom ID
 
@@ -949,7 +949,7 @@ To use this component, you need to send the [message flag](/docs/resources/messa
 | type         | integer                                                                         | `11` for thumbnail component                                                    |
 | id?          | integer                                                                         | Optional identifier for component                                               |
 | media        | [unfurled media item](/docs/components/reference#unfurled-media-item-structure) | A url or attachment                                                             |
-| description? | string                                                                          | Alt text for the media                                                          |
+| description? | string                                                                          | Alt text for the media, max 1024 characters                                     |
 | spoiler?     | boolean                                                                         | Whether the thumbnail should be a spoiler (or blurred out). Defaults to `false` |
 
 ###### Example
@@ -979,7 +979,7 @@ To use this component, you need to send the [message flag](/docs/resources/messa
 | Field        | Type                                                                            | Description                                                                 |
 |--------------|---------------------------------------------------------------------------------|-----------------------------------------------------------------------------|
 | media        | [unfurled media item](/docs/components/reference#unfurled-media-item-structure) | A url or attachment                                                         |
-| description? | string                                                                          | Alt text for the media                                                      |
+| description? | string                                                                          | Alt text for the media, max 1024 characters                                 |
 | spoiler?     | boolean                                                                         | Whether the media should be a spoiler (or blurred out). Defaults to `false` |
 
 ###### Example
@@ -1209,6 +1209,8 @@ To upload a file with your message, you'll need to send your payload as `multipa
 
 Before the introduction of the `IS_COMPONENTS_V2` flag ([see changelog](/docs/change-log/2025-04-22-components-v2)), message components were sent in conjunction with message content. This means that you could send a message using a subset of the available components without setting the `IS_COMPONENTS_V2` flag, and the components would be included in the message content along with `content` and `embeds`.
 
+Additionally, components of messages preceding components V2 will contain an `id` of `0`.
+
 Apps using this Legacy Message Component behavior will continue to work as expected, but it is recommended to use the new `IS_COMPONENTS_V2` flag for new apps or features as they offer more options for layout and customization.
 
 :::info