fix(cli): use uv tool upgrade when Hermes is a uv tool install (#29700)

Hermes installed via `uv tool install hermes-agent` lives outside any
venv. `_cmd_update_pip` previously ran `uv pip install --upgrade`, which
errors with `No virtual environment found; run uv venv ...`. The user
hits this on the very first `hermes update` after a standard
non-`--system` install with `uv` on PATH.

Add `is_uv_tool_install()` in `hermes_cli/config.py`: fast path inspects
`sys.prefix` for the standard `uv/tools/hermes-agent/` layout, falls
back to `uv tool list` for non-standard prefixes. Both the
user-facing `recommended_update_command_for_method("pip")` string and
the actual subprocess invocation in `_cmd_update_pip` now switch to
`uv tool upgrade hermes-agent` when detected. Non-tool installs and the
no-`uv` fallback keep their existing commands unchanged.

hermes_cli/main.py

@@ -8971,13 +8971,17 @@ def cmd_update(args):
 def _cmd_update_pip(args):
     """Update Hermes via pip (for PyPI installs)."""
     from hermes_cli import __version__
+    from hermes_cli.config import is_uv_tool_install
 
     print(f"→ Current version: {__version__}")
     print("→ Checking PyPI for updates...")
 
     uv = shutil.which("uv")
     if uv:
-        cmd = [uv, "pip", "install", "--upgrade", "hermes-agent"]
+        if is_uv_tool_install(uv):
+            cmd = [uv, "tool", "upgrade", "hermes-agent"]
+        else:
+            cmd = [uv, "pip", "install", "--upgrade", "hermes-agent"]
     else:
         cmd = [sys.executable, "-m", "pip", "install", "--upgrade", "hermes-agent"]