fix(agents): sign-in hint names the CLI the IDE actually runs (#2018)

Fixes #1913. The sign-in hint named the bare command (`cursor-agent login`), but the IDE launches agents through its own resolution (registry installs under the config dir, the login shell's PATH, PATHEXT shims), so the named command could be missing from the terminal's PATH. The agent spec is now resolved once before connecting, and when that executable isn't what a PATH lookup of the bare name finds, every built-in hint names the resolved path, quoted for PowerShell or POSIX shells. Hints for separate login tools (claude-acp, codex-acp, vibe) and custom agents are unchanged; the hint is translated through templates.

src/platform/locales/text/en.json

@@ -1,4 +1,7 @@
 {
+  "Run `{command}` in a terminal.": "Run `{command}` in a terminal.",
+  "Run `{command}` in a terminal and sign in.": "Run `{command}` in a terminal and sign in.",
+  "{name} needs you to sign in. {hint}": "{name} needs you to sign in. {hint}",
   "OpenIDEA or JetBrains settings": "OpenIDEA or JetBrains settings",
   "Import JetBrains Settings": "Import JetBrains Settings",
   "These settings will be imported:": "These settings will be imported:",

src/platform/locales/text/zh.json

@@ -1,4 +1,7 @@
 {
+  "Run `{command}` in a terminal.": "在终端中运行 `{command}`。",
+  "Run `{command}` in a terminal and sign in.": "在终端中运行 `{command}` 并登录。",
+  "{name} needs you to sign in. {hint}": "{name} 需要你登录。{hint}",
   "Cannot copy reference": "无法复制引用",
   "Group actions": "分组操作",
   "New Project Group": "新建项目组",