nvim: dim the minuet ghost text below comment brightness

minuet links MinuetVirtualText -> Comment, which in vague is #606079 -- the
same colour as real comments, so a suggestion reads as if it were already part
of the file. Dropped to #4a4a5c, between Comment and Whitespace (#333738).

⚠ Re-applied on ColorScheme. Loading a colourscheme runs ,
which drops custom groups, so setting this once at startup works until the
first :colorscheme and then silently stops. The reference values for the
palette are in the comment so the number can be tuned without going and
looking them up again.

common/nvim/init.lua

@@ -231,6 +231,31 @@ minuet.setup({
 })
 end
 
+-- Ghost text, dimmer than a comment.
+--
+-- minuet links MinuetVirtualText -> Comment, which in `vague` is #606079 --
+-- the same colour as real comments, so a suggestion reads as if it were
+-- already part of the file. This drops it toward the background.
+--
+-- Reference points in this colourscheme, for tuning:
+--   Normal     #cdcdcd   (actual code)
+--   Comment    #606079   (minuet's default -- too prominent)
+--   MINUET     #4a4a5c   <- here
+--   Whitespace #333738   (about as dim as stays legible)
+--
+-- ⚠ MUST be re-applied on ColorScheme. Loading a colourscheme runs
+-- `highlight clear`, which drops custom groups -- so setting this once at
+-- startup works until the first `:colorscheme` and then silently stops.
+local MINUET_FG = "#4a4a5c"
+local function minuet_highlight()
+    vim.api.nvim_set_hl(0, "MinuetVirtualText", { fg = MINUET_FG, italic = true })
+end
+vim.api.nvim_create_autocmd("ColorScheme", {
+    group = vim.api.nvim_create_augroup("MinuetHighlight", { clear = true }),
+    callback = minuet_highlight,
+})
+minuet_highlight()
+
 -- Registered UNCONDITIONALLY, so it can report the case where the plugin
 -- itself is missing. A status command that only exists when everything
 -- already works is not a status command.