Stop Generate from going silent: merge watchdog-arm into the click event

Two prior attempts (removing then reworking the standalone fn=None
.then() step) didn't fix it — Generate still never reached the backend
after the button changed state, meaning that whole extra chain link was
the problem, not its inputs value.

Verified in Gradio's own source (events.py): js "runs before fn" on the
SAME event when both are given — it isn't a separate chain link. Moved
the watchdog-arm js= directly onto the existing .click(fn=_btn_generating)
call instead of chaining a standalone fn=None step after it. This
removes the untested fn=None/non-queued link from the chain entirely
rather than trying to fix its behavior.

app.py

@@ -3161,11 +3161,7 @@ with gr.Blocks(title="Generate Audio for Video", css=_SLOT_CSS, js=_GLOBAL_JS) a
                 fn=_btn_generating,
                 inputs=None,
                 outputs=[taro_btn],
-            ).then(
-                fn=None,
-                inputs=[],
-                outputs=[],
-                js="() => window._armGenerateWatchdog('taro_btn', 600000)",
+                js="() => { window._armGenerateWatchdog('taro_btn', 600000); }",
             ).then(
                 fn=_run_taro,
                 inputs=[taro_video, taro_seed, taro_cfg, taro_steps, taro_mode,
@@ -3232,11 +3228,7 @@ with gr.Blocks(title="Generate Audio for Video", css=_SLOT_CSS, js=_GLOBAL_JS) a
                 fn=_btn_generating,
                 inputs=None,
                 outputs=[mma_btn],
-            ).then(
-                fn=None,
-                inputs=[],
-                outputs=[],
-                js="() => window._armGenerateWatchdog('mma_btn', 600000)",
+                js="() => { window._armGenerateWatchdog('mma_btn', 600000); }",
             ).then(
                 fn=_run_mmaudio,
                 inputs=[mma_video, mma_prompt, mma_neg, mma_seed,
@@ -3302,11 +3294,7 @@ with gr.Blocks(title="Generate Audio for Video", css=_SLOT_CSS, js=_GLOBAL_JS) a
                 fn=_btn_generating,
                 inputs=None,
                 outputs=[hf_btn],
-            ).then(
-                fn=None,
-                inputs=[],
-                outputs=[],
-                js="() => window._armGenerateWatchdog('hf_btn', 600000)",
+                js="() => { window._armGenerateWatchdog('hf_btn', 600000); }",
             ).then(
                 fn=_run_hunyuan,
                 inputs=[hf_video, hf_prompt, hf_neg, hf_seed,