fix(desktop): keep tab strip when preview/Browser is open

[HexLab98]

Summary

• Sticky "Hide tab bar" could leave an in-app Browser/preview open with no tab strip and no close control.
• Closeable main tiles (preview / Browser / session) now keep the strip visible so the close affordance stays available.
• Tool-only zones still honor a deliberate sticky hide.

Test plan

• npx vitest run src/components/pane-shell/tree/renderer/lone-header.test.ts src/components/pane-shell/tree/tool-pane-toggle.test.ts (from apps/desktop)
• In Hermes Desktop: open an HTML/URL preview, hide the tab bar (or double-tap the strip), confirm the strip/close control returns while the preview is open
• Hide the tab bar on a tools-only zone (terminal/logs), close and re-open a tool pane, confirm sticky hide still sticks
• Lone chat workspace still auto-hides the strip when no preview/session tile is open

[OutThisLife]

Your resolveZoneHeaderHidden is the right shape — a closeable main tile has to outrank the hidden flag, and pulling the precedence into one function is what the inline expression in TreeGroup was missing.

#91714 arrives at the same design and generalizes it: one resolver both the renderer and the store call, with the hidden flag itself replaced by a tri-state mode so a repair can no longer overwrite a preference. Credited in the description. Closing in favor of that.