fix(cli): preserve -t/-m/--provider/--tui/--dev before chat subcommand

`hermes -t web chat` silently dropped the toolset filter (and the same
hold true for `-m`, `--provider`, `--tui`, `--dev` placed before
`chat`). Reported in #28780 for `-t/--toolsets`; the others are sibling
failures with the same root cause.

Root cause: the chat subparser re-declared these flags with `default=None`
(or `default=False` for store_true) on top of the matching top-level
parser flags. When argparse dispatches into the subparser it shares the
namespace via `dest`, so the subparser's default overwrites whatever the
top-level parser parsed before the subcommand. `-s/--skills`, `-r/-c/-w`,
`--yolo`, and `--pass-session-id` already use `default=argparse.SUPPRESS`
for exactly this reason — the chat-subparser action becomes a no-op
unless the user explicitly passes the flag after `chat`, and the parent
value survives.

Reproduction (origin/main, before fix):

  >>> parser.parse_known_args(["-t", "web", "chat"]).toolsets
  None
  >>> parser.parse_known_args(["chat", "-t", "web"]).toolsets
  'web'

After fix:

  >>> parser.parse_known_args(["-t", "web", "chat"]).toolsets
  'web'
  >>> parser.parse_known_args(["chat", "-t", "web"]).toolsets
  'web'

Sibling flags fixed in the same commit because they share the exact same
argparse pattern bug — verified via a new contract test that scans every
chat-subparser action whose `dest` is also on the top-level parser and
asserts `default is argparse.SUPPRESS`. The test fails on origin/main
listing all five offenders and passes after this fix.

Test additions in tests/hermes_cli/test_argparse_flag_propagation.py:
- TestChatSubparserInheritedValueFlags exercising real `_parser` build
  (not the hand-rolled replica) so it catches future drift.
- Parametrized before-chat / after-chat cases for `-t`, `--toolsets`,
  `-m`, `--model`, `--provider`.
- Negative case: passing none of the flags leaves attrs at the top-level
  parser's `None` default (SUPPRESS does not remove existing attrs).
- Combined case: all three value flags before `chat` simultaneously.
- store_true cases for `--tui` / `--dev`.
- Contract test asserting every shared-`dest` flag on chat uses SUPPRESS.

Fixes #28780.

hermes_cli/_parser.py

@@ -271,12 +271,27 @@ def build_top_level_parser():
     chat_parser.add_argument(
         "--image", help="Optional local image path to attach to a single query"
     )
+    # `default=argparse.SUPPRESS` on flags that are ALSO declared on the
+    # top-level parser: when the user writes `hermes -m foo chat`, argparse
+    # first sets `args.model = "foo"` from the top-level parser, then
+    # dispatches to the chat subparser. Without SUPPRESS the chat subparser's
+    # own default (`None`) would silently clobber the top-level value because
+    # the subparser shares the same namespace and `dest`. SUPPRESS keeps the
+    # subparser action a no-op unless the user actually passes the flag after
+    # the subcommand. Matches the pattern already used for `-s/--skills` and
+    # the relaunch-inherited flags `-r/--resume`, `-c/--continue`,
+    # `-w/--worktree`, `--yolo`, etc. (see tests/hermes_cli/
+    # test_argparse_flag_propagation.py).
     _inherited_flag(
         chat_parser,
-        "-m", "--model", help="Model to use (e.g., anthropic/claude-sonnet-4)",
+        "-m", "--model",
+        default=argparse.SUPPRESS,
+        help="Model to use (e.g., anthropic/claude-sonnet-4)",
     )
     chat_parser.add_argument(
-        "-t", "--toolsets", help="Comma-separated toolsets to enable"
+        "-t", "--toolsets",
+        default=argparse.SUPPRESS,
+        help="Comma-separated toolsets to enable",
     )
     _inherited_flag(
         chat_parser,
@@ -293,7 +308,7 @@ def build_top_level_parser():
         # are also valid values, and runtime resolution (resolve_runtime_provider)
         # handles validation/error reporting consistently with the top-level
         # `--provider` flag.
-        default=None,
+        default=argparse.SUPPRESS,
         help="Inference provider (default: auto). Built-in or a user-defined name from `providers:` in config.yaml.",
     )
     chat_parser.add_argument(
@@ -401,14 +416,14 @@ def build_top_level_parser():
         chat_parser,
         "--tui",
         action="store_true",
-        default=False,
+        default=argparse.SUPPRESS,
         help="Launch the modern TUI instead of the classic REPL",
     )
     _inherited_flag(
         chat_parser,
         "--cli",
         action="store_true",
-        default=False,
+        default=argparse.SUPPRESS,
         help="Force the classic prompt_toolkit REPL (overrides display.interface=tui)",
     )
     _inherited_flag(
@@ -416,7 +431,7 @@ def build_top_level_parser():
         "--dev",
         dest="tui_dev",
         action="store_true",
-        default=False,
+        default=argparse.SUPPRESS,
         help="With --tui: run TypeScript sources via tsx (skip dist build)",
     )