fix(tmux): forward nav keys directly to mux pane on Windows (psmux)

On Windows with psmux, control keys like C-j passed through Neovim's
terminal emulation get mangled (C-j/newline becomes CR/submit). Route
nav key passthrough via tmux send-key when a mux parent is available,
bypassing the terminal translation layer.

Sanitize session names (spaces to hyphens) and sync mux_session so
tmux send-keys targets the correct session on psmux.

Author: John Mutuma (from Dev Box)

lua/sidekick/cli/actions.lua

@@ -47,6 +47,16 @@ local function nav(dir)
   return function(terminal)
     local at_edge = vim.fn.winnr() == vim.fn.winnr(dir)
     if at_edge or terminal:is_float() then
+      -- When running under a mux backend (e.g., tmux via psmux on Windows),
+      -- returning the key as an expr string passes through Neovim's terminal
+      -- emulation, which can mangle control characters (e.g., C-j becomes CR).
+      -- Send the key directly to the mux pane instead.
+      if terminal.parent and terminal.parent.send_key then
+        vim.schedule(function()
+          terminal.parent:send_key(("C-%s"):format(dir))
+        end)
+        return
+      end
       return ("<c-%s>"):format(dir)
     end
     vim.schedule(function()

lua/sidekick/cli/session/tmux.lua

@@ -30,18 +30,20 @@ end
 ---@return sidekick.cli.terminal.Cmd?
 function M:start()
   if not self.external then
-    local cmd = { "tmux", "new", "-A", "-s", self.id }
+    -- Sanitize session name: replace spaces with hyphens for psmux/Windows compatibility
+    local session_name = self.id:gsub("%s+", "-")
+    self.mux_session = session_name
+    local cmd = { "tmux", "new", "-A", "-s", session_name }
     vim.list_extend(cmd, { "-c", self.cwd })
     self:add_cmd(cmd)
     if vim.fn.has("win32") == 1 then
       -- On Windows (psmux), ";" command chaining is not supported.
       -- PowerShell interprets ";" as a statement separator, causing
       -- "set-option" to be run as a standalone cmdlet (which fails).
       -- Instead, run set-option as separate commands after the session starts.
-      local id = self.id
       vim.defer_fn(function()
-        vim.fn.system({ "tmux", "set-option", "-t", id, "status", "off" })
-        vim.fn.system({ "tmux", "set-option", "-t", id, "detach-on-destroy", "on" })
+        vim.fn.system({ "tmux", "set-option", "-t", session_name, "status", "off" })
+        vim.fn.system({ "tmux", "set-option", "-t", session_name, "detach-on-destroy", "on" })
       end, 1000)
     else
       vim.list_extend(cmd, { ";", "set-option", "status", "off" })
@@ -198,6 +200,14 @@ function M:submit()
   Util.exec({ "tmux", "send-keys", "-t", self.tmux_pane_id, "Enter" })
 end
 
+---Send a raw key to a tmux pane
+---@param key string tmux key name (e.g., "C-j", "Enter", "Escape")
+function M:send_key(key)
+  if self.mux_session then
+    Util.exec({ "tmux", "send-keys", "-t", self.mux_session, key })
+  end
+end
+
 function M:dump()
   local pane_id = self:pane_id()
   if not pane_id then