Add Plot Output 1D tab for transect visualization with unified interface

[Copilot]

Adds a new tab to visualize 1D transects (cross-sections) of model output along user-selectable positions. Renames existing "Plot Output" tab to "Plot Output 2D" for clarity. Both tabs now feature a unified interface with dynamic variable dropdowns and consistent behavior.

Changes

UI Components

• 1D Tab: NetCDF file browser with dynamic variable dropdown, transect direction selector (cross-shore/along-shore), interactive sliders for position and time
• 2D Tab: Updated to match 1D interface with variable dropdown, single "Load & Plot" button, and overlay vegetation checkbox
• Dynamic Variables: Both tabs automatically populate dropdowns with available variables from NetCDF file, filtering out coordinates and metadata
• Matplotlib visualization with automatic coordinate handling (2D/1D arrays, grid indices)

Implementation (aeolis/gui.py)

• Renamed create_plot_output_tab() → create_plot_output_2d_tab()
• Added 1D tab with 8 methods for creation, file I/O, and plot updates
• Added 2D tab methods: plot_nc_2d(), update_2d_plot(), on_variable_changed_2d()
• Simplified update_time_step() to use unified plotting approach
• Real-time plot refresh on variable/position/time changes in both tabs

Bug Fixes

• Fixed transect direction scrolling error (IndexError when x and y dimensions differ)
• Slider range now reconfigures automatically when changing direction
• Variable dropdowns only show valid 2D/3D data variables (excludes x, y, s, n, time, bounds, etc.)

Code Quality

• Fixed platform-specific path separators (os.pardir + os.sep instead of ..\\..\\)
• Added dimension validation (requires 3D for time-varying, 2D for static variables)
• Empty dictionary checks before access

Example Usage:

# Cross-shore transect: fix y-index=75, vary along x (s dimension)
transect_data = var_data[time_idx, 75, :]

# Along-shore transect: fix x-index=150, vary along y (n dimension)  
transect_data = var_data[time_idx, :, 150]

~545 lines added/modified in aeolis/gui.py. No breaking changes. Both tabs now provide consistent user experience with dynamic variable discovery.

Original prompt

add a "Plot Output 1D" tab that handles plotting zb and all the other parameters in the current "plot output" tab in a transect that can be selected by the user. Change the name of the current "Plot output" tab in "Plot Output 2D".

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[Sierd]

@copilot Only show the available variables in the dropdown menu of the 'Plot Output 1D' tab. Adapt the 'Plot Output 2D' tab to use the dropdown menu for selected variables in the same fashion as the 'Plot Output 1D' tab. Update the plotting area accoordingly by replacing all buttons with a 'load and plot'. The code gives an error when when scrolling through the transect direction. I think this is because x and y have different lenghts (the error points out line 830 in gui.py that gives an error)

[Copilot]

@copilot Only show the available variables in the dropdown menu of the 'Plot Output 1D' tab. Adapt the 'Plot Output 2D' tab to use the dropdown menu for selected variables in the same fashion as the '...

Fixed all issues in commit 74edae0:

1. Fixed transect direction scrolling error (line 830)

• Slider range now reconfigures when changing direction
• Prevents IndexError when x and y dimensions differ
• Automatically adjusts slider value if out of bounds

2. Dynamic variable dropdowns

• Both tabs now show only available variables from NetCDF file
• Excludes coordinate/metadata variables (x, y, s, n, time, etc.)
• Automatically populated when loading file

3. Unified 2D tab interface

• Added variable dropdown matching 1D tab style
• Replaced 4 buttons with single "Load & Plot" button
• Added "Overlay vegetation" checkbox
• Variable changes update plot immediately

See mockup showing updated interface for both tabs.