helium/core: add "mute tab" action to tab context menu

[saberoueslati]

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Tested on (check one or more):

• Windows
• macOS
• Linux

---

Closes #974

Adds a "Mute tab" / "Unmute tab" toggle to the tab context menu, placed next to the existing "Mute site" item. Operates on the individual tab's audio mute state independently of site-level muting.

• New CommandToggleTabAudioMuted command added to TabStripModelCommand enum
• WillContextMenuMuteTab() added to TabStripModel to drive the label toggle
• IDS_TAB_CXMENU_SOUND_MUTE_TAB / IDS_TAB_CXMENU_SOUND_UNMUTE_TAB strings added to generated_resources.grd
• Menu item wired through tab_menu_model.cc
• ToggleTabAudioMuted histogram variant added to histograms.xml

Video of the manual test on Windows below :

Enregistrement.2026-05-23.142504.mp4

I'll be testing this also on Linux and update the description if it goes fine

Edit :

Works also on Linux, video of the manual testing below :

Screencast.from.2026-05-23.23-24-10.webm

[greptile-apps]

_{Reviews (1): Last reviewed commit: "Correct i8n issue" | Re-trigger Greptile}

[greptile-apps]

The ToggleTabAudioMuted variant is placed after ToggleVertical, but alphabetically ToggleTab... should precede ToggleVer.... Chromium histogram tooling often enforces sorted variant lists, and an out-of-order entry can cause PRESUBMIT or lint failures at build time.

Suggested change

	<variant name="ToggleMuted" summary="the Toggle muted command"/>
	<variant name="TogglePinned" summary="the Toggle Pinned command"/>
	<variant name="ToggleVertical" summary="the Toggle Vertical tabs command"/>
	+ <variant name="ToggleTabAudioMuted"
	+ summary="the Toggle Tab Audio Muted command"/>
	</variants>
	<variant name="ToggleMuted" summary="the Toggle muted command"/>
	<variant name="TogglePinned" summary="the Toggle Pinned command"/>
	+ <variant name="ToggleTabAudioMuted"
	+ summary="the Toggle Tab Audio Muted command"/>
	<variant name="ToggleVertical" summary="the Toggle Vertical tabs command"/>
	</variants>