fix(channels,sandbox): land hard breakage cluster from reviewed PR bases

Lands reviewed fixes based on #25839 (@pewallin), #25841 (@joshjhall), and #25737/@25713 (@DennisGoldfinger/@peteragility), with additional hardening + regression tests for queue cleanup and shell script safety.

Fixes #25836
Fixes #25840
Fixes #25824
Fixes #25868

Co-authored-by: Peter Wallin <pwallin@gmail.com>
Co-authored-by: Joshua Hall <josh@yaplabs.com>
Co-authored-by: Dennis Goldfinger <dennisgoldfinger@gmail.com>
Co-authored-by: peteragility <peteragility@users.noreply.github.com>

src/discord/monitor/message-handler.process.ts

@@ -564,9 +564,8 @@ export async function processDiscordMessage(ctx: DiscordMessagePreflightContext)
     humanDelay: resolveHumanDelayConfig(cfg, route.agentId),
     deliver: async (payload: ReplyPayload, info) => {
       const isFinal = info.kind === "final";
-      if (info.kind === "block") {
-        // Block payloads carry reasoning/thinking content that should not be
-        // delivered to external channels. Skip them regardless of streamMode.
+      if (payload.isReasoning) {
+        // Reasoning/thinking payloads should not be delivered to Discord.
         return;
       }
       if (draftStream && isFinal) {