feat(gateway): expose plugin slash commands natively on all platforms + decision-capable command hook

Plugin slash commands now surface as first-class commands in every gateway
enumerator — Discord native slash picker, Telegram BotCommand menu, Slack
/hermes subcommand map — without a separate per-platform plugin API.

The existing 'command:<name>' gateway hook gains a decision protocol via
HookRegistry.emit_collect(): handlers that return a dict with
{'decision': 'deny'|'handled'|'rewrite'|'allow'} can intercept slash
command dispatch before core handling runs, unifying what would otherwise
have been a parallel 'pre_gateway_command' hook surface.

Changes:

- gateway/hooks.py: add HookRegistry.emit_collect() that fires the same
  handler set as emit() but collects non-None return values. Backward
  compatible — fire-and-forget telemetry hooks still work via emit().
- hermes_cli/plugins.py: add optional 'args_hint' param to
  register_command() so plugins can opt into argument-aware native UI
  registration (Discord arg picker, future platforms).
- hermes_cli/commands.py: add _iter_plugin_command_entries() helper and
  merge plugin commands into telegram_bot_commands() and
  slack_subcommand_map(). New is_gateway_known_command() recognizes both
  built-in and plugin commands so the gateway hook fires for either.
- gateway/platforms/discord.py: extract _build_auto_slash_command helper
  from the COMMAND_REGISTRY auto-register loop and reuse it for
  plugin-registered commands. Built-in name conflicts are skipped.
- gateway/run.py: before normal slash dispatch, call emit_collect on
  command:<canonical> and honor deny/handled/rewrite/allow decisions.
  Hook now fires for plugin commands too.
- scripts/release.py: AUTHOR_MAP entry for @Magaav.
- Tests: emit_collect semantics, plugin command surfacing per platform,
  decision protocol (deny/handled/rewrite/allow + non-dict tolerance),
  Discord plugin auto-registration + conflict skipping, is_gateway_known_command.

Salvaged from #14131 (@Magaav). Original PR added a parallel
'pre_gateway_command' hook and a platform-keyed plugin command
registry; this re-implementation reuses the existing 'command:<name>'
hook and treats plugin commands as platform-agnostic so the same
capability reaches Telegram and Slack without new API surface.

Co-authored-by: Magaav <73175452+Magaav@users.noreply.github.com>

hermes_cli/commands.py

@@ -260,6 +260,26 @@ GATEWAY_KNOWN_COMMANDS: frozenset[str] = frozenset(
 )
 
 
+def is_gateway_known_command(name: str | None) -> bool:
+    """Return True if ``name`` resolves to a gateway-dispatchable slash command.
+
+    This covers both built-in commands (``GATEWAY_KNOWN_COMMANDS`` derived
+    from ``COMMAND_REGISTRY``) and plugin-registered commands, which are
+    looked up lazily so importing this module never forces plugin
+    discovery. Gateway code uses this to decide whether to emit
+    ``command:<name>`` hooks — plugin commands get the same lifecycle
+    events as built-ins.
+    """
+    if not name:
+        return False
+    if name in GATEWAY_KNOWN_COMMANDS:
+        return True
+    for plugin_name, _description, _args_hint in _iter_plugin_command_entries():
+        if plugin_name == name:
+            return True
+    return False
+
+
 # Commands with explicit Level-2 running-agent handlers in gateway/run.py.
 # Listed here for introspection / tests; semantically a subset of
 # "all resolvable commands" — which is the real bypass set (see
@@ -371,12 +391,47 @@ def gateway_help_lines() -> list[str]:
     return lines
 
 
+def _iter_plugin_command_entries() -> list[tuple[str, str, str]]:
+    """Yield (name, description, args_hint) tuples for all plugin slash commands.
+
+    Plugin commands are registered via
+    :func:`hermes_cli.plugins.PluginContext.register_command`. They behave
+    like ``CommandDef`` entries for gateway surfacing: they appear in the
+    Telegram command menu, in Slack's ``/hermes`` subcommand mapping, and
+    (via :func:`gateway.platforms.discord._register_slash_commands`) in
+    Discord's native slash command picker.
+
+    Lookup is lazy so importing this module never forces plugin discovery
+    (which can trigger filesystem scans and environment-dependent
+    behavior).
+    """
+    try:
+        from hermes_cli.plugins import get_plugin_commands
+    except Exception:
+        return []
+    try:
+        commands = get_plugin_commands() or {}
+    except Exception:
+        return []
+    entries: list[tuple[str, str, str]] = []
+    for name, meta in commands.items():
+        if not isinstance(name, str) or not isinstance(meta, dict):
+            continue
+        description = str(meta.get("description") or f"Run /{name}")
+        args_hint = str(meta.get("args_hint") or "").strip()
+        entries.append((name, description, args_hint))
+    return entries
+
+
 def telegram_bot_commands() -> list[tuple[str, str]]:
     """Return (command_name, description) pairs for Telegram setMyCommands.
 
     Telegram command names cannot contain hyphens, so they are replaced with
     underscores.  Aliases are skipped -- Telegram shows one menu entry per
     canonical command.
+
+    Plugin-registered slash commands are included so plugins get native
+    autocomplete in Telegram without touching core code.
     """
     overrides = _resolve_config_gates()
     result: list[tuple[str, str]] = []
@@ -386,6 +441,10 @@ def telegram_bot_commands() -> list[tuple[str, str]]:
         tg_name = _sanitize_telegram_name(cmd.name)
         if tg_name:
             result.append((tg_name, cmd.description))
+    for name, description, _args_hint in _iter_plugin_command_entries():
+        tg_name = _sanitize_telegram_name(name)
+        if tg_name:
+            result.append((tg_name, description))
     return result
 
 
@@ -750,6 +809,9 @@ def slack_subcommand_map() -> dict[str, str]:
 
     Maps both canonical names and aliases so /hermes bg do stuff works
     the same as /hermes background do stuff.
+
+    Plugin-registered slash commands are included so ``/hermes <plugin-cmd>``
+    routes through the plugin handler.
     """
     overrides = _resolve_config_gates()
     mapping: dict[str, str] = {}
@@ -759,6 +821,9 @@ def slack_subcommand_map() -> dict[str, str]:
         mapping[cmd.name] = f"/{cmd.name}"
         for alias in cmd.aliases:
             mapping[alias] = f"/{alias}"
+    for name, _description, _args_hint in _iter_plugin_command_entries():
+        if name not in mapping:
+            mapping[name] = f"/{name}"
     return mapping