Migrate the replies, pinned messages and send reaction responses to the generated responses

[gpunto]

Goal

Parse the replies, pinned messages and send reaction responses with the generated response models.

Part of AND-1291

Implementation

• The four replies endpoints return GetRepliesResponse, pinned messages returns GetPinnedMessagesResponse and send reaction returns SendReactionResponse.
• Delete the hand-written MessagesResponse and ReactionResponse envelopes. The messages and reactions inside were already generated models, so call sites don't change.
• All three responses now require duration, and the send reaction response also requires message. The backend always sends both.

Testing

MessageListResponseParsingTest covers each response, a missing duration and a send reaction response without its message. MoshiChatApiTest rows cover the new response types.

On a device: loaded replies through all four variants, loaded pinned messages and sent a reaction. Message order, pinned state, reaction type, score and user, and custom data round-trips all matched.

🤖 Generated with Claude Code

[github-actions]

PR checklist ✅

All required conditions are satisfied:

• Title length is OK (or ignored by label).
• At least one pr: label exists.
• Sections ### Goal, ### Implementation, and ### Testing are filled, or the PR is bot-authored.
• An issue is linked (Linear ticket or GitHub issue), or the PR is bot-authored.

🎉 Great job! This PR is ready for review.

[github-actions]

SDK Size Comparison 📏

SDK	Before	After	Difference	Status
stream-chat-android-client	6.17 MB	6.17 MB	0.00 MB	🟢
stream-chat-android-ui-components	11.48 MB	11.48 MB	0.00 MB	🟢
stream-chat-android-compose	13.14 MB	13.14 MB	0.00 MB	🟢

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud