fix: prevent agent badge clipping and portal tabs into titlebar

[heyramzi]

Summary

Two titlebar layout fixes:

1. Agent badge clipping

The active-agent badge ("● 1 active") was rendered inside the sidebar-width-constrained container with overflow-hidden, causing it to get clipped when the sidebar is narrow.

Fix: Moved the badge out of the constrained container so it sits as a direct child of the titlebar flex row. Added flex-shrink: 0 to prevent compression.

Before:

The badge text gets cut off — "1 active" becomes "1 activ..."

2. Tabs in titlebar (save vertical space)

The titlebar row was entirely empty in its center section (#titlebar-tabs was an invisible spacer), while tabs rendered in a separate 36px row below it — wasting vertical screen real estate.

Fix: When there are no split groups, the tab bar is portaled into the titlebar's #titlebar-tabs slot via createPortal, so the titlebar doubles as the tab strip. When splits are active, each group renders its own inline tab bar as before — avoiding the visual "jump" issue noted in the previous implementation.

Changes

File	What
App.tsx	Moved agent badge outside sidebar-width container; updated #titlebar-tabs to accept portaled tabs with items-stretch
TabGroupPanel.tsx	Portal tab bar into #titlebar-tabs when !hasSplitGroups; fall back to inline rendering for splits
main.css	Added flex-shrink: 0 to badge; added #titlebar-tabs > .terminal-tab-strip no-drag rule for portaled tabs

Test plan

• Open Orca with a narrow sidebar — verify the agent badge ("● N active") is fully visible and not clipped
• Toggle showTitlebarAgentActivity off in Settings → Appearance — badge should disappear
• With a single worktree (no splits): tabs should render in the titlebar row, no separate tab strip below
• Create a split (⌘D or drag): both groups should show their own inline tab bars
• Close the split: tabs should portal back into the titlebar
• Verify tabs are clickable and scrollable when in the titlebar (no drag region interference)

[nwparker]

Thanks @heyramzi

We made some changes here to re-work the split pane work... but 100% agreed this is real.
In fact, we did a temporary revert, but will re-work these changes into our feature re-work

cc @brennanb2025

[AmethystLiang]

This issue has been fixed in other PRs. Closing this one now.

Thx for putting it up though!