docs: fully document draft/channel-rename (RENAME syntax, permissions, PART/JOIN fallback, registered-channel rule) + a notable-capabilities section

content/docs/commands.md

@@ -31,7 +31,7 @@ require `+o` and may be further restricted by your oper type (see [Operators](/d
 | `INVITE` / `UNINVITE` | Invite or revoke a pending invite |
 | `KNOCK` | Request an invite to an invite-only channel |
 | `CYCLE` | Part and immediately rejoin |
-| `RENAME` | Rename a channel (op+) |
+| `RENAME` | Rename a channel in place (op+) — see [Channel rename](/docs/ircv3#channel-rename) |
 | `TBAN` | Set a temporary, auto-expiring channel ban |
 | `NAMES` | List channel members |
 | `MODE` | Query or change channel/user modes |

content/docs/ircv3.md

@@ -47,4 +47,55 @@ SASL mechanism list, enabled sub-features) to CAP-302 clients.
 | `draft/filehost` | Advertise an external file-host + signed upload links |
 | `no-implicit-names` | Suppress the automatic NAMES burst on JOIN |
 
+## Notable capabilities
+
+A few of these do more than the one-line table can show.
+
+### Channel rename
+
+The `draft/channel-rename` capability lets a channel **operator** rename a channel in place, keeping
+its membership, modes, topic, bans and timestamp:
+
+```text
+RENAME <#old> <#new> [<reason>]
+```
+
+Members whose client negotiated the capability get a single `RENAME` message and stay in the channel
+seamlessly. Members without it are moved with an automatic **PART + JOIN** (topic and names
+preserved), so their client follows the channel too. A change that only alters the *case* of the name
+needs no move at all.
+
+The server enforces a few rules:
+
+- you must be a channel **operator** (or an IRC operator);
+- the channel **prefix** can't change (`#foo` → `&foo` is refused);
+- the new name must be valid and **not already in use**, and can't be `CBAN`'d (operators bypass that);
+- a **registered (`+r`) channel** is owned by services — a client can't rename it; ask ChanServ
+  (`/msg ChanServ RENAME <#channel> <#newname>`), which does it over the server link. Operators may
+  rename registered channels directly.
+
+Failures come back as standard replies, e.g. `FAIL RENAME CANNOT_RENAME …` or
+`FAIL RENAME CHANNEL_NAME_IN_USE …`.
+
+### Message history
+
+`draft/chathistory` replays a channel's or DM's recent messages from the server's per-conversation
+store (the `CHATHISTORY` command). With `draft/event-playback` the replay also carries
+JOIN/PART/QUIT/NICK/MODE/TOPIC/KICK events, so a reconnecting client rebuilds the whole picture.
+
+### Multiline messages
+
+`draft/multiline` sends a message that spans several lines as one logical message, wrapped in a
+`BATCH`; the advertised `max-bytes` / `max-lines` limits are configurable.
+
+### Web Push
+
+`draft/webpush` registers an RFC 8291 / 8292 subscription (the `WEBPUSH` command) so a highlight or
+private message reaches a client whose tab is backgrounded or away — even when it isn't connected.
+
+### STS
+
+`sts` advertises a strict-transport-security policy on the plaintext port so capable clients upgrade
+to TLS and pin it for a configured duration.
+
 For SASL mechanisms, see [Accounts & SASL](/docs/accounts).