fix(ui): drop noisy colorcolumn, polish highlights, warn on missing colorscheme

The full-column ColorColumn was visually overwhelming on every line, especially
with default vim's LightRed (kicked in silently when solarized8 wasn't installed).
Replace it with an OverLength match that only highlights characters past the
buffer's textwidth.

- editing.vim: OverLength matchadd, refreshed on FileType/BufWinEnter/OptionSet
- languages.vim: drop colorcolumn from per-filetype autocmds (textwidth still set)
- ui.vim: VertSplit/CursorLine/CursorLineNr/SignColumn override via ColorScheme
  autocmd; fillchars for vert and eob; timer-based warning if solarized8 missing

modules/editing.vim

@@ -44,3 +44,26 @@ augroup ChopstickSearchHL
     autocmd!
     autocmd CursorHold * if get(v:, 'hlsearch', 0) | let v:hlsearch = 0 | endif
 augroup END
+
+" ── Overlength Highlight (only chars past textwidth, not the whole column) ─
+
+function! s:OverLengthApply() abort
+    if exists('w:overlength_match')
+        silent! call matchdelete(w:overlength_match)
+        unlet w:overlength_match
+    endif
+    if &textwidth <= 0 || &buftype !=# '' | return | endif
+    let w:overlength_match = matchadd('OverLength', '\%>' . &textwidth . 'v.\+', -1)
+endfunction
+
+function! s:OverLengthDefineHL() abort
+    hi default OverLength ctermbg=52 ctermfg=NONE guibg=#3a1f1f guifg=NONE
+endfunction
+
+augroup ChopstickOverLength
+    autocmd!
+    autocmd ColorScheme    * call s:OverLengthDefineHL()
+    autocmd OptionSet      textwidth call s:OverLengthApply()
+    autocmd BufWinEnter,WinEnter,FileType * call s:OverLengthApply()
+augroup END
+call s:OverLengthDefineHL()

modules/languages.vim

@@ -47,23 +47,23 @@ augroup ChopstickFiletype
         \ if line("'\"") > 1 && line("'\"") <= line("$") | exe "normal! g'\"" | endif
 
     autocmd FileType python
-        \ setlocal expandtab shiftwidth=4 tabstop=4 textwidth=88 colorcolumn=+1
+        \ setlocal expandtab shiftwidth=4 tabstop=4 textwidth=88
     autocmd FileType javascript,typescript
-        \ setlocal expandtab shiftwidth=2 tabstop=2 textwidth=100 colorcolumn=+1
+        \ setlocal expandtab shiftwidth=2 tabstop=2 textwidth=100
     autocmd FileType go
-        \ setlocal noexpandtab shiftwidth=4 tabstop=4 textwidth=120 colorcolumn=+1
+        \ setlocal noexpandtab shiftwidth=4 tabstop=4 textwidth=120
     autocmd FileType rust
-        \ setlocal expandtab shiftwidth=4 tabstop=4 textwidth=100 colorcolumn=+1
+        \ setlocal expandtab shiftwidth=4 tabstop=4 textwidth=100
     autocmd FileType c,cpp
-        \ setlocal expandtab shiftwidth=4 tabstop=4 textwidth=80 colorcolumn=+1
+        \ setlocal expandtab shiftwidth=4 tabstop=4 textwidth=80
     autocmd FileType html,css
         \ setlocal expandtab shiftwidth=2 tabstop=2
     autocmd FileType yaml
         \ setlocal expandtab shiftwidth=2 tabstop=2
     autocmd FileType markdown
-        \ setlocal wrap linebreak spell textwidth=0 colorcolumn=0 conceallevel=2
+        \ setlocal wrap linebreak spell textwidth=0 conceallevel=2
     autocmd FileType sh
-        \ setlocal expandtab shiftwidth=2 tabstop=2 textwidth=80 colorcolumn=+1
+        \ setlocal expandtab shiftwidth=2 tabstop=2 textwidth=80
     autocmd FileType make
         \ setlocal noexpandtab shiftwidth=8 tabstop=8
     autocmd FileType json

modules/ui.vim

@@ -10,16 +10,49 @@ endif
 
 set background=dark
 
+function! s:WarnSolarized8Missing(...) abort
+    echohl WarningMsg
+    echom 'chopsticks: solarized8 not installed — run :PlugInstall'
+    echohl None
+endfunction
+
 if !g:is_tty
     try
         colorscheme solarized8
-    catch
+    catch /^Vim\%((\a\+)\)\=:E185/
         colorscheme default
+        if has('timers')
+            call timer_start(500, function('s:WarnSolarized8Missing'))
+        else
+            augroup ChopstickColorschemeWarn
+                autocmd!
+                autocmd VimEnter * call s:WarnSolarized8Missing()
+            augroup END
+        endif
     endtry
 else
     colorscheme default
 endif
 
+" ── Window separators, fillchars, cursorline visibility ────────────────────
+
+if !g:is_tty
+    set fillchars+=vert:│,eob:\
+endif
+
+function! s:UIPolish() abort
+    hi VertSplit    ctermbg=234 ctermfg=240 guibg=#002b36 guifg=#586e75 cterm=NONE gui=NONE
+    hi CursorLine   ctermbg=235             guibg=#0c4452                cterm=NONE gui=NONE
+    hi CursorLineNr ctermbg=235 ctermfg=136 guibg=#0c4452 guifg=#b58900  cterm=bold gui=bold
+    hi SignColumn   ctermbg=234             guibg=#002b36
+endfunction
+
+augroup ChopstickUIPolish
+    autocmd!
+    autocmd ColorScheme * call s:UIPolish()
+augroup END
+if !g:is_tty | call s:UIPolish() | endif
+
 if has("gui_running")
     if has("gui_gtk2") || has("gui_gtk3")
         set guifont=Hack\ 12,Source\ Code\ Pro\ 12,Monospace\ 12