feat(pane-nav): add multiplexer-aware pane navigation

lua/plugins/pane-nav.lua

@@ -0,0 +1,29 @@
+--- <C-h/j/k/l> pane navigation that follows whatever multiplexer Neovim is
+--- running under (herdr, tmux, or bare kitty) — see config.pane_nav.
+---
+--- This replaces AstroNvim's smart-splits mappings on the same keys (which only
+--- know tmux/wezterm/kitty and would move the wrong layer inside herdr).
+--- smart-splits itself stays for the <C-Up/Down/Left/Right> resize mappings.
+
+local nav = require "config.pane_nav"
+
+--- AstroNvim's key spelling for these chords, so the entries overwrite rather
+--- than race the smart-splits / term_nav mappings.
+local moves = {
+  ["<C-H>"] = "left",
+  ["<C-J>"] = "down",
+  ["<C-K>"] = "up",
+  ["<C-L>"] = "right",
+}
+
+return {
+  "AstroNvim/astrocore",
+  opts = function(_, opts)
+    local maps = opts.mappings
+    for key, dir in pairs(moves) do
+      local desc = ("Move %s a split (%s aware)"):format(dir, nav.env())
+      maps.n[key] = { function() nav.navigate(dir) end, desc = desc }
+      maps.t[key] = { nav.terminal(dir), desc = desc }
+    end
+  end,
+}