Fix deprecated avifile/addframe API and timeseries_extract_slice returning all zeros

[Copilot]

movie_tools and movie_of_slice_timeseries used the removed avifile()/addframe() API. timeseries_extract_slice returned all zeros due to double spm_vol remapping and was missing sagittal/coronal implementations entirely.

timeseries_extract_slice.m

• Replaced broken delegation chain (get_ax_slice → spm_vol → spm_slice_vol) with direct inline extraction using the spm_matrix + spm_slice_vol pattern from the working timeseries4.m
• Added sagittal and coronal slice extraction (previously referenced but undefined)
• Removed stale SPM version detection boilerplate

get_ax_slice.m

• Replaced manual eye(4) + C(3,4) = slice_num with spm_matrix([0 0 slice_num]), consistent with cluster_orthviews.m
• Use V(i).dim(1:2) per-volume instead of pre-computed V(1).dim(1:2)

movie_of_slice_timeseries.m

• writeVideo(mov, H) passed a raw axes handle — fixed to writeVideo(mov, getframe(H))
• mov.Quality was a bare property read (no-op) — fixed to mov.Quality = 75
• Updated unused add_a_frame helper to match

movie_tools.m

• Replaced avifile()/addframe() with VideoWriter/open/writeVideo/getframe in the 'avi' branch

% Before
mov = avifile('mymovie.avi', 'Quality', 75, 'Compression', 'None', 'Fps', fps);
mov = addframe(mov, H);

% After
mov = VideoWriter('mymovie.avi');
mov.Quality = 75;
mov.FrameRate = fps;
open(mov);
frame = getframe(H);
writeVideo(mov, frame);

Original prompt

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This section details on the original issue you should resolve

<issue_title>movie_tools and movie_of_slice_timeseries calls deprecated avifile() function. timeseries_extract_slice returns all 0s.</issue_title>
<issue_description>movie_tools and movie_of_slice_timeseries are no longer functional because avifile() has been replaced by writeVideo().

timeseries_extract_slice, which is called in movie_of_slice_timeseries, returns all 0s.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes movie_tools and movie_of_slice_timeseries calls deprecated avifile() function. timeseries_extract_slice returns all 0s. #57

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