fix(help): better align local-additions #38097

Problem:
Descriptions of plugins often contain taglinks which are generally
concealed. This misaligns them by 2 characters with descriptions that
don't have a taglink in them.

Solution:
Don't count "bar" characters (`|`) for the description width.

Example:

Actual buffer content:
```
myplugin.txt                  |lsp| is cool
myplugin.txt        this is a nice plugin
```

Rendered as:
```
myplugin.txt                  lsp is cool
myplugin.txt        this is a nice plugin
```

runtime/lua/vim/_core/help.lua

@@ -175,7 +175,8 @@ function M.local_additions()
       if plugname and desc then
         -- left-align taglink and right-align description by inserting spaces in between
         local plug_width = vim.fn.strdisplaywidth(plugname)
-        local desc_width = vim.fn.strdisplaywidth(desc)
+        local _, concealed_chars = desc:gsub('|', '')
+        local desc_width = vim.fn.strdisplaywidth(desc) - concealed_chars
         -- max(l, 1) forces at least one space for if the description is too long
         local spaces = string.rep(' ', math.max(textwidth - desc_width - plug_width - 2, 1))
         local fmt = string.format('|%s|%s%s', plugname, spaces, desc)

src/gen/gen_help_html.lua

@@ -173,11 +173,23 @@ local function url_encode(s)
 end
 
 local function to_titlecase(s)
-  local text = ''
+  local special = {
+    ['UI'] = true,
+    ['API'] = true,
+    ['TUI'] = true,
+    ['LSP'] = true,
+    ['TS'] = true,
+  }
+  ---@type string[]
+  local text = {}
   for w in vim.gsplit(s, '[ \t]+') do
-    text = ('%s %s%s'):format(text, vim.fn.toupper(w:sub(1, 1)), w:sub(2))
+    local sub = vim.fn.toupper(w:sub(1, 1)) .. w:sub(2):lower()
+    if special[w:upper()] then
+      sub = w:upper()
+    end
+    text[#text + 1] = sub
   end
-  return text
+  return table.concat(text, ' ')
 end
 
 local function to_heading_tag(text)
@@ -588,7 +600,7 @@ local function visit_node(root, level, lang_tree, headings, opt, stats)
     end
     -- Remove tags from ToC text.
     local heading_node = first(root, 'heading')
-    local hname = trim(node_text(heading_node):gsub('%*.*%*', ''))
+    local hname = to_titlecase(trim(node_text(heading_node):gsub('%*.*%*', '')))
     if not heading_node or hname == '' then
       return '' -- Spurious "===" or "---" in the help doc.
     end
@@ -606,7 +618,12 @@ local function visit_node(root, level, lang_tree, headings, opt, stats)
       )
     end
     local el = node_name == 'h1' and 'h2' or 'h3'
-    return ('<%s id="%s" class="help-heading">%s</%s>\n'):format(el, tagname, trimmed, el)
+    return ('<%s id="%s" class="help-heading">%s</%s>\n'):format(
+      el,
+      tagname,
+      to_titlecase(trimmed),
+      el
+    )
   elseif node_name == 'heading' then
     return trimmed
   elseif node_name == 'column_heading' or node_name == 'column_name' then