feat: add 'View full command' option to dangerous command approval

When a dangerous command is detected and the user is prompted for
approval, long commands are truncated (80 chars in fallback, 70 chars
in the TUI). Users had no way to see the full command before deciding.

This adds a 'View full command' option across all approval interfaces:

- CLI fallback (tools/approval.py): [v]iew option in the prompt menu.
  Shows the full command and re-prompts for approval decision.
- CLI TUI (cli.py): 'Show full command' choice in the arrow-key
  selection panel. Expands the command display in-place and removes
  the view option after use.
- CLI callbacks (callbacks.py): 'view' choice added to the list when
  the command exceeds 70 characters.
- Gateway (gateway/run.py): 'full', 'show', 'view' responses reveal
  the complete command while keeping the approval pending.

Includes 7 new tests covering view-then-approve, view-then-deny,
short command fallthrough, and double-view behavior.

Closes community feedback about the 80-char cap on dangerous commands.

hermes_cli/callbacks.py

@@ -105,10 +105,14 @@ def approval_callback(cli, command: str, description: str) -> str:
     """Prompt for dangerous command approval through the TUI.
 
     Shows a selection UI with choices: once / session / always / deny.
+    When the command is longer than 70 characters, a "view" option is
+    included so the user can reveal the full text before deciding.
     """
     timeout = 60
     response_queue = queue.Queue()
     choices = ["once", "session", "always", "deny"]
+    if len(command) > 70:
+        choices.append("view")
 
     cli._approval_state = {
         "command": command,