fix(slack): guard split()[0] against whitespace-only command text

When a user sends a Slack message like '/hermes   ' (trailing whitespace
after the slash) the legacy subcommand router hit `text.split()[0]` with
a truthy-but-whitespace-only `text`. `'   '.split()` returns `[]` →
IndexError, blowing up the slash handler before fallthrough to `/help`.

Switch to a two-step guard that materializes the parts list first and
indexes only if non-empty.

Salvaged from PR #2752 by @nidhi-singh02. The PR's other two hunks
(`tools/file_operations.py`, `agent/anthropic_adapter.py`) are
unreachable in current code — `LINTERS` is a hardcoded constant dict
with no empty values, and the anthropic version-detection site is
already guarded by a `result.stdout.strip()` truthy check — so only the
slack hunk is taken.

Closes #2745

Co-authored-by: Teknium <127238744+teknium1@users.noreply.github.com>

gateway/platforms/slack.py

@@ -2785,7 +2785,10 @@ class SlackAdapter(BasePlatformAdapter):
             from hermes_cli.commands import slack_subcommand_map
             subcommand_map = slack_subcommand_map()
             subcommand_map["compact"] = "/compress"
-            first_word = text.split()[0] if text else ""
+            # Guard against whitespace-only text where ``text`` is truthy but
+            # ``text.split()`` returns ``[]`` (e.g. user sends ``/hermes   ``).
+            parts = text.split() if text else []
+            first_word = parts[0] if parts else ""
             if first_word in subcommand_map:
                 rest = text[len(first_word):].strip()
                 text = f"{subcommand_map[first_word]} {rest}".strip() if rest else subcommand_map[first_word]