feat(ui): native tabline + fixed-width signcolumn

Show all listed buffers in a tabline (current bufnr highlighted, modified
marker '+'), and reserve a permanent signcolumn so width doesn't jitter when
gitgutter/ALE/LSP signs come and go.

- ui.vim: TLBuild() + TabLine{,Sel,Fill} hl groups via ColorScheme autocmd;
  set signcolumn=yes for non-TTY (overrides core.vim's previous logic)
- core.vim: drop non-TTY signcolumn branch (centralized in ui.vim)

modules/core.vim

@@ -178,13 +178,8 @@ set shortmess+=cI
 if g:is_tty
     set signcolumn=auto
     set synmaxcol=120
-else
-    if has("patch-8.1.1564")
-        set signcolumn=number
-    else
-        set signcolumn=yes
-    endif
 endif
+" non-TTY signcolumn is set in ui.vim (=yes, fixed-width to prevent jitter)
 
 " ── Project-Local Config ────────────────────────────────────────────────────
 

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
@@ -151,3 +184,43 @@ set statusline=%!SLBuild()
 if g:is_tty
     set statusline=%f\ %h%w%m%r\ %=%(%l,%c%V\ %=\ %P%)
 endif
+
+" ── Tabline (native — shows listed buffers when >1, else hidden) ───────────
+
+function! s:TLDefineColors() abort
+    hi TabLine     ctermbg=234 ctermfg=244 cterm=none guibg=#002b36 guifg=#839496 gui=none
+    hi TabLineSel  ctermbg=235 ctermfg=136 cterm=bold guibg=#073642 guifg=#b58900 gui=bold
+    hi TabLineFill ctermbg=234 ctermfg=240 cterm=none guibg=#002b36 guifg=#586e75 gui=none
+endfunction
+
+augroup TLColors
+    autocmd!
+    autocmd ColorScheme * call s:TLDefineColors()
+augroup END
+call s:TLDefineColors()
+
+function! TLBuild() abort
+    let l:s = ''
+    let l:cur = bufnr('%')
+    for l:b in range(1, bufnr('$'))
+        if !buflisted(l:b) || getbufvar(l:b, '&buftype') !=# '' | continue | endif
+        let l:hl   = (l:b == l:cur) ? '%#TabLineSel#' : '%#TabLine#'
+        let l:name = bufname(l:b)
+        let l:name = empty(l:name) ? '[No Name]' : fnamemodify(l:name, ':t')
+        let l:mod  = getbufvar(l:b, '&modified') ? ' +' : ''
+        let l:s .= l:hl . ' ' . l:b . ' ' . l:name . l:mod . ' '
+    endfor
+    let l:s .= '%#TabLineFill#%='
+    return l:s
+endfunction
+
+if !g:is_tty
+    set showtabline=1
+    set tabline=%!TLBuild()
+endif
+
+" ── SignColumn: always reserve a column so width never jitters ─────────────
+
+if !g:is_tty
+    set signcolumn=yes
+endif