themes: one file each, generated from helix and zed, picked by stepping a list

Each theme is a .zig file of pure data and nothing enumerates them by hand —
fold() walks the container's declarations, so a theme is a file and that is the
whole registration. Field by field rather than a wholesale coercion, which
makes a missing field a compile error that names it.

tools/gen_themes.zig reads helix .toml and zed .json out of vendor/themes and
emits one .zig each; build.zig reads that directory, so adding a theme is
dropping a file in. Output goes to the build cache rather than the tree, so zig
owns the freshness check and a deleted source cannot leave a stale theme
behind. Vendored, not read from the genizah: the build stays offline. A source
it cannot map is a hard error naming the file and the key, never a silently
black-on-black theme.

ThemeSel is the clever half. Traits gained an `executes` column, so n/N over
that buffer hands the whole line to Exec instead of the leading word to Look —
both arms the ordinary builtin, so a stepped row does exactly what the matching
mouse button on it would. Stepping the list previews each theme live. The trait
is a pane property, not an output-pane branch, so any pane whose lines are
commands can opt in.

Goldens: leader gains SPC t t; theme's fourth NextColor no longer wraps to
helix because the ring is fifteen long. New: themesel.

1 files changed, 1 insertions, 1 deletions

diff --git a/next-steps.txt b/next-steps.txt
index a230beca..9cc22419 100644
--- a/next-steps.txt
+++ b/next-steps.txt
@@ -4,7 +4,7 @@
 - Add multiple cursor support, and Ctrl-c auto comments. Use the same methodology of running helix in a harness as the oracle for differential testing. Also add regex interactive selection like on helix and the more specific selection semantics, use https://github.com/mnemnion/mvzr for regexes, add it using zig fetch.
 - Add a new builtin that will list all builtins and their respective shortcuts if they have any (note that shortcuts may be spc+... or just keyboard or mouse chords/movements)
 - Scrolling on a touchpad moves horizontally accidentally way too much, add some heuristics to prioritize vertical scrolling and make horizontal scrolling work only when the user is a bit more explicit about it - for example by measuring if there was recent high-enough vertical movement, etc.
-- Add a new builtin to list the themes and create an output window to select those themes; each theme now must live on its own .zig file, when moving with n/N on out ThemeSel output window it will select that theme so it's a interactive way to select the themes. We're being clever now with how these output windows will work, this feature depends on the new semantics for output windows but basically now the ThemeSel output panes will set the Command flag that will basically tell that when doing n/N movement on the output pane instead of Look-ing it will Execute the line, so the ThemeSel output pane will be like: (Theme acme, Theme a, Theme b) seperated by lines so the n/N will automatically consider selecting the Theme + argument (this is not output pane specific, it should be generalized to work on every pane kind), and will Exec it. Add new themes that will be automatically exported from helix and zed, a new binary will execute that will generate .zig files, this binary will be added as a execute step on the build.zig so when building it will regenarate those .zig that will be then included on the runtime as themes.
++ Add a new builtin to list the themes and create an output window to select those themes; each theme now must live on its own .zig file, when moving with n/N on out ThemeSel output window it will select that theme so it's a interactive way to select the themes. We're being clever now with how these output windows will work, this feature depends on the new semantics for output windows but basically now the ThemeSel output panes will set the Command flag that will basically tell that when doing n/N movement on the output pane instead of Look-ing it will Execute the line, so the ThemeSel output pane will be like: (Theme acme, Theme a, Theme b) seperated by lines so the n/N will automatically consider selecting the Theme + argument (this is not output pane specific, it should be generalized to work on every pane kind), and will Exec it. Add new themes that will be automatically exported from helix and zed, a new binary will execute that will generate .zig files, this binary will be added as a execute step on the build.zig so when building it will regenarate those .zig that will be then included on the runtime as themes.
 - Use zig's 0.16 new threaded io and the std functions that the build system uses to listen for file changes, it needs to use something from the os so it's not a busy wait. It will only track files on open panes. when a file is updated, doing Undo will return to the state that it was before so if a file automatically updates the user won't lose the unsaved state as it was before and the editor won't need to handle with merging the unsaved changes and the new update.
 - There's some bug when rendering from a ssh session - the screen gets dirty with old chars when scrolling.
 - There's some bad performance when dealing with specially large files or long lines; write a perf harness for this and optimize the performance.