Open agent browsers in the right panel when "Auto-show floating preview" is off

[Mikiyas-Meles-Assefa]

I keep Auto-show floating preview turned off because I'd rather keep previews in the right panel. For devices that already works: when an agent opens one, it shows up as a right-panel tab, like docs/user/devices.md says.

Browsers don't do that. When an agent opens a browser with the setting off, nothing shows up unless the agent forces it, and then it pops up in the floating player anyway. So I end up hunting for the tab to see what the agent is doing.

Would you be open to browsers following the same rule as devices? Floating when the setting is on, a right-panel tab when it's off, and sheet layouts left alone. The tab would open as an automatic update like the device one does, so it wouldn't stop the turn diff or a linked PR from opening in the panel.

I have a small change for this locally (in revealServerTabs and rightPanelStore, with tests). Happy to open it as a PR with screenshots if this sounds like the right direction.

[Entrpi]

A related angle, with a working branch: let the agent choose where its tab goes when the user asks. Today an agent cannot put a browser tab in the right panel or move one there, even when the user asks for exactly that ("open the dev server in the browser sidebar"). Every reveal floats.

• preview_open gets an optional placement: "panel" | "floating". Left unset, nothing changes, including what happens with the setting off, so it fits with the default change proposed here. Set, the tab opens there, or an open tab moves there: the same move as the user's "Open in right panel" and "Float preview over chat".
• Panel placements open as an automatic update, through an automatic flag on rightPanelStore.openBrowser and close, like openDevice. So they do not take focus or stop the turn diff or a PR from opening in the panel. That is the same flag your change needs, so the two would share it.
• Mobile ignores it, because it has no right panel.
• Cost: 229 more bytes in the MCP tool list.
• Evals, 3 samples each: "open the dev server in the browser sidebar" and "move that preview into the right sidebar" went from 0/3 to 3/3 on Claude Sonnet 5.5, Claude Opus 5.5 and GPT-6.1 Sol. A guard case checks that models leave placement unset when the user did not ask.

Branch: main...Entrpi:t3code:fix/preview-open-placement

Would you want this alongside the default change here?