fix(chat): send button should use system theme variables (#55075)

Merged via squash.

Prepared head SHA: eb3e197874
Co-authored-by: bottenbenny <270688955+bottenbenny@users.noreply.github.com>
Co-authored-by: velvet-shark <126378+velvet-shark@users.noreply.github.com>
Reviewed-by: @velvet-shark

CHANGELOG.md

@@ -48,6 +48,7 @@ Docs: https://docs.openclaw.ai
 - Claude CLI: switch the bundled Claude CLI backend to `stream-json` output so watchdogs see progress on long runs, and keep session/usage metadata even when Claude finishes with an empty result line. (#49698) Thanks @felear2022.
 - Claude CLI/MCP: always pass a strict generated `--mcp-config` overlay for background Claude CLI runs, including the empty-server case, so Claude does not inherit ambient user/global MCP servers. (#54961) Thanks @markojak.
 - Agents/embedded replies: surface mid-turn 429 and overload failures when embedded runs end without a user-visible reply, while preserving successful media-only replies that still use legacy `mediaUrl`. (#50930) Thanks @infichen.
+- Chat/UI: move the chat send button onto the shared ghost-button theme styling, while keeping the stop button icon readable on the danger state. (#55075) Thanks @bottenbenny.
 - WhatsApp/allowFrom: show a specific allowFrom policy error for valid blocked targets instead of the misleading `<E.164|group JID>` format hint. Thanks @mcaxtr.
 - Agents/cooldowns: scope rate-limit cooldowns per model so one 429 no longer blocks every model on the same auth profile, replace the exponential 1 min -> 1 h escalation with a stepped 30 s / 1 min / 5 min ladder, and surface a user-facing countdown message when all models are rate-limited. (#49834) Thanks @kiranvk-2011.
 - Agents/embedded transport errors: distinguish common network failures like connection refused, DNS lookup failure, and interrupted sockets from true timeouts in embedded-run user messaging and lifecycle diagnostics. (#51419) Thanks @scoootscooob.

ui/src/styles/chat/layout.css

@@ -497,13 +497,13 @@
   height: 30px;
   border-radius: var(--radius-md);
   border: none;
-  background: var(--muted-strong);
-  color: var(--text-strong);
+  background: transparent;
+  color: var(--muted);
   cursor: pointer;
   flex-shrink: 0;
   transition:
     background var(--duration-fast) ease,
-    box-shadow var(--duration-fast) ease;
+    color var(--duration-fast) ease;
   padding: 0;
 }
 
@@ -518,8 +518,8 @@
 }
 
 .chat-send-btn:hover:not(:disabled) {
-  background: var(--muted);
-  box-shadow: none;
+  color: var(--text);
+  background: var(--bg-hover);
 }
 
 .chat-send-btn:disabled {
@@ -529,6 +529,7 @@
 
 .chat-send-btn--stop {
   background: var(--danger);
+  color: var(--destructive-foreground);
 }
 
 .chat-send-btn--stop:hover:not(:disabled) {