feat(gateway): per-platform admin/user split for slash commands (salvage of #4443) (#23373)

* feat(gateway): per-platform admin/user split for slash commands

Adds an opt-in two-list access control on top of the existing per-platform
`allow_from` allowlists, scoped to slash commands only:

  - allow_admin_from         — full slash command access
  - user_allowed_commands    — what non-admins may run
  - group_allow_admin_from   — same, group/channel scope
  - group_user_allowed_commands

When `allow_admin_from` is unset for a scope, gating is disabled and every
allowed user keeps full access (backward compat). Plain chat is unaffected.
`/help` and `/whoami` are always reachable so users can see what they
can run.

Gate runs at the slash command dispatch site in gateway/run.py and uses
`is_gateway_known_command()`, so it covers built-in AND plugin-registered
commands through the live registry without per-feature wiring.

Adds `/whoami` showing platform, scope, tier, and runnable commands.

Salvage of PR #4443's permission tier work, scoped down. The full tier
system, tool filtering, audit log, usage tracking, rate limiting,
`/promote` flow, and persistent SQLite stores are not included here —
those can be re-expanded later if needed.

Co-authored-by: ReqX <mike@grossmann.at>

* fix(gateway): close running-agent fast-path bypass + add coverage and central docs

The slash command access gate was only applied at the cold dispatch site
(line ~5921). When an agent was already running, the running-agent
fast-path block (line ~5574) dispatched /restart, /stop, /new, /steer,
/model, /approve, /deny, /agents, /background, /kanban, /goal, /yolo,
/verbose, /footer, /help, /commands, /profile, /update directly
without going through the gate — letting non-admins bypass gating just
because an agent happens to be busy.

Refactored the gate into _check_slash_access() and called from BOTH
paths. /status remains intentionally pre-gate so users can always see
session state.

Also added 18 more dispatch tests covering:
  - Running-agent fast-path: blocks non-admin, allows admin, /status
    always works
  - Alias canonicalization (gate uses canonical name, not user alias)
  - Unknown / unregistered commands pass through (don't false-positive)
  - DM admin scope-locked when group has its own admin list
  - Multi-platform isolation (Discord gated, Telegram unrestricted)

Docs: added Slash Command Access Control section to the central
messaging index page + /whoami row in the chat commands table.

Co-authored-by: ReqX <mike@grossmann.at>

---------

Co-authored-by: ReqX <mike@grossmann.at>

website/docs/user-guide/messaging/telegram.md

@@ -685,6 +685,50 @@ TELEGRAM_GROUP_ALLOWED_USERS="-1001234567890"
 TELEGRAM_GROUP_ALLOWED_CHATS="-1001234567890"
 ```
 
+## Slash Command Access Control
+
+By default, every allowed user can run every slash command. To split your allowlist into **admins** (full slash command access) and **regular users** (only commands you explicitly enable), add `allow_admin_from` and `user_allowed_commands` to the platform's `extra` block:
+
+```yaml
+gateway:
+  platforms:
+    telegram:
+      extra:
+        # Existing allowlists (unchanged)
+        allow_from:
+          - "123456789"     # admin
+          - "555555555"     # regular user
+          - "777777777"     # regular user
+
+        # NEW — admins get all slash commands (built-in + plugin)
+        allow_admin_from:
+          - "123456789"
+
+        # NEW — non-admin allowed users can only run these slash commands.
+        # /help and /whoami are always allowed so users can see their access.
+        user_allowed_commands:
+          - status
+          - model
+          - history
+
+        # Optional: separate admin/command lists for groups
+        group_allow_admin_from:
+          - "123456789"
+        group_user_allowed_commands:
+          - status
+```
+
+**Behavior:**
+
+- A user listed in `allow_admin_from` for a scope (DM or group) can run **every** registered slash command — built-in commands AND plugin-registered ones — through the live registry.
+- A user in `allow_from` but **not** in `allow_admin_from` can only run commands listed in `user_allowed_commands`, plus the always-allowed floor: `/help` and `/whoami`.
+- Plain chat (non-slash messages) is unaffected. Non-admin users can still talk to the agent normally, they just can't trigger arbitrary commands.
+- **Backward compat:** if `allow_admin_from` is not set for a scope, slash command gating is disabled for that scope. Existing installs keep working with no changes.
+- DM admin status does not imply group admin status. Each scope has its own admin list.
+- If only `group_allow_admin_from` is set, DM scope stays in unrestricted (backward-compat) mode.
+
+Use `/whoami` to see the active scope, your tier (admin / user / unrestricted), and which slash commands you can run.
+
 ## Interactive Model Picker
 
 When you send `/model` with no arguments in a Telegram chat, Hermes shows an interactive inline keyboard for switching models: