fix(chat): anchor modal to floating button

[ComputelessComputer]

Align the floating chat panel to the bottom FAB line and cover the placement with a focused component test.

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Note

Medium Risk
Touches floating chat layout, resize math, and tab/chatMode coupling across navigation paths; regressions could affect panel placement or when chat stays open, but behavior is covered by new tests.

Overview
The floating chat panel is bottom-anchored to the FAB line (items-end, transformOrigin: bottom center), with layout driven by a dedicated container rect that uses the floating anchor and, when expanded, stretches to the root container bottom while staying aligned to the anchor.

Resize behavior adds top and corner handles, adjusts handle hit areas, fixes vertical resize to follow pointer movement (not symmetric doubling), and shows corner grip indicators; expanded state clears when the panel hides.

Tab store auto-collapses floating chat when you open, select, or cycle to a different session (or close the active session and land on another); reopening the same session leaves chat open. Toolbar and empty-state tweaks trim icons and polish expand/chat-title controls.

New persistent-chat component tests cover anchoring, resize handles, expand alignment, and expanded reset on close; chat-mode tests cover session-navigation collapse rules.

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[cursor]

Cursor Bugbot has reviewed your changes and found 2 potential issues.

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