fix: three CLI quality-of-life fixes (#10468, #10230, #10526, #9545) (#10599)

Three independent fixes batched together:

1. hermes auth add crashes on non-interactive stdin (#10468)
   input() for the label prompt was called without checking isatty().
   In scripted/CI environments this raised EOFError. Fix: check
   sys.stdin.isatty() and fall back to the computed default label.

2. Subcommand help prints twice (#10230)
   'hermes dashboard -h' printed help text twice because the
   SystemExit(0) from argparse was caught by the fallback retry
   logic, which re-parsed and printed help again. Fix: re-raise
   SystemExit with code 0 (help/version) immediately.

3. Duplicate entries in /model picker (#10526, #9545)
   - Kimi showed 2x because kimi-coding and kimi-coding-cn both
     mapped to the same models.dev ID. Fix: track seen mdev_ids
     and skip aliases.
   - Providers could show 2-3x from case-variant slugs across the
     four loading paths. Fix: normalize all seen_slugs membership
     checks and insertions to lowercase.

Closes #10468, #10230, #10526, #9545

hermes_cli/main.py

@@ -6325,8 +6325,13 @@ Examples:
             sys.stderr = _io.StringIO()
             args = parser.parse_args(_processed_argv)
             sys.stderr = _saved_stderr
-        except SystemExit:
+        except SystemExit as exc:
             sys.stderr = _saved_stderr
+            # Help/version flags (exit code 0) already printed output —
+            # re-raise immediately to avoid a second parse_args printing
+            # the same help text again (#10230).
+            if exc.code == 0:
+                raise
             # Subcommand name was consumed as a flag value (e.g. -c model).
             # Fall back to optional subparsers so argparse handles it normally.
             subparsers.required = False