refactor!: Migrate runners cmd from string to argv (#134)

Migrate command execution to structured argv lists across the plugin, replacing shell-string command construction with `vim.system` argv execution. The runner API now exposes argv-based execution as the default path:

   - `runner.execute_command` -> `runner.execute`
   - `runner.execute_command_async` -> `runner.execute_async`
   - `runner.execute_command_raw` -> `runner.execute_raw`
   - `runner.execute_command_raw_async` -> `runner.execute_raw_async`
   - `runner.execute_command_sync` was removed; use `runner.execute` and handle the result directly

BREAKING CHANGES:
   - `cmd.new({ args = ... })` now requires `args` as `string[]` argv tokens, not a single string.
   - `cmd.log({ ... })` now uses `raw_flags` as `string[]` for raw passthrough flags; `raw = "..."` is no longer supported.
   - Direct users of `jj.core.runner` must migrate from the old `execute_command*` string helpers to the new argv-based `execute*` helpers.

lua/jj/cmd/resolve.lua

@@ -1,6 +1,7 @@
 local M = {}
 
 local utils = require("jj.utils")
+local jj_args = require("jj.core.args")
 local terminal = require("jj.ui.terminal")
 local runner = require("jj.core.runner")
 
@@ -16,27 +17,22 @@ function M.resolve(opts)
 		return
 	end
 
-	local cmd_args = { "jj", "resolve", "--revision", rev }
+	local cmd = { "jj", "resolve", "--revision", rev }
 	-- Extra arguments
-	vim.list_extend(cmd_args, args)
-	-- Append the filestes
-	for _, fileset in ipairs(filesets) do
-		table.insert(cmd_args, utils.escape_fileset(fileset))
-	end
+	vim.list_extend(cmd, args)
 
-	local escaped_cmd_args = {}
-	for _, arg in ipairs(cmd_args) do
-		table.insert(escaped_cmd_args, vim.fn.shellescape(arg))
+	-- Append filesets as jj string literal
+	for _, fileset in ipairs(filesets) do
+		table.insert(cmd, jj_args.fileset(fileset))
 	end
-	local shell_cmd = table.concat(escaped_cmd_args, " ")
 
 	utils.notify(string.format("Resolving conflicts in change `%s`...", rev), vim.log.levels.INFO)
 
 	-- If external is set, run the command asynchronously and invoke the on_exit callback if provided
 	if opts.external then
 		-- Run the command asynchronously and notify the user of the result
-		runner.execute_command_async(
-			shell_cmd,
+		runner.execute_async(
+			cmd,
 			function(output)
 				if output and output ~= "" then
 					utils.notify(output, vim.log.levels.INFO)
@@ -56,7 +52,7 @@ function M.resolve(opts)
 		)
 	else
 		-- Otherwise, run in a floating terminal
-		terminal.run_floating(cmd_args, nil, {
+		terminal.run_floating(cmd, nil, {
 			title = " JJ Resolve ",
 			modifiable = true,
 			keep_modifiable = true,