**Plan**

1. **DeviiTerminal.js – Titlebar double-click**  
   - In the titlebar dblclick handler (add `stopPropagation()` after the maximize toggle) to prevent the document dblclick handler from firing.  
   - Also check that the document dblclick handler only triggers close when the click target is **not** inside the `<devii-terminal>` element (i.e., truly outside the window), so double-clicking the titlebar never leads to a close.

2. **FloatingWindow.js – ResizeObserver guard during transitions**  
   - Add a `_transitioning` flag that is set `true` at the start of any state change (in `_setState`) and reset `false` after the CSS transition ends (listen for `transitionend` event on `this.win`).  
   - Inside `_observeResize`, skip the geometry capture if `this._transitioning` is true.  
   - Alternatively, disable the CSS `width`/`height` transition during state changes by toggling a class, but the flag + `transitionend` is simpler and preserves animation for other properties.

3. **Optional (improves UX but not required by ticket):** Fix the launcher FAB CSS in `devii.css` (line 108) to show the FAB when Devii is closed. This prevents the user from being forced to double-click to reopen, but is a separate concern and can be omitted if the plan must stay minimal.

**Definition of done**  
- Titlebar double-click **maximizes/normalizes** the window; the window does **not** close.  
- Double-clicking outside the window (on the document) correctly **closes** Devii (existing behaviour preserved).  
- After closing and reopening Devii, the window geometry is **unchanged** from before the close.  
- Repeating the cycle (open → double-click titlebar → close → reopen) does **not** progressively shrink the window; size remains stable.  
- All existing tests pass: `pip install -e '.[dev]' -q && python -m pytest {test_files}` (where `{test_files}` is the full test suite, e.g., `tests/`).  
- No regressions in other Devii window interactions (resize, drag, state transitions).