docs: replace !gh command with slash/context-menu commands

Document the /gh login, /gh logout and /gh comment add|edit|del
commands plus the right-click message context-menu equivalents, and
require the applications.commands invite scope. Comments are posted as
the linked user's own GitHub account, so the old GitHub App identity,
Message Content intent and Read Message History requirements are gone.

README.md

@@ -167,10 +167,10 @@ Add the bot to your server with the `bot` scope and the following permissions:
 
 Combined permission integer: `274877910016`
 
-Invite URL (replace `CLIENT_ID` with your bot's client ID):
+Invite URL (replace `CLIENT_ID` with your bot's client ID). The `applications.commands` scope is required so the slash / context-menu commands can be registered:
 
 ```
-https://discord.com/oauth2/authorize?client_id=YOUR_BOT_CLIENT_ID&permissions=274877910016&scope=bot
+https://discord.com/oauth2/authorize?client_id=YOUR_BOT_CLIENT_ID&permissions=274877910016&scope=bot+applications.commands
 ```
 
 ### Intents
@@ -184,24 +184,38 @@ The Discord Gateway connection only keeps the bot showing as **online** — it i
 - `DISCORD_GATEWAY_ENABLED=false` (default): messages are sent directly via REST; the Gateway is not connected.
 - `DISCORD_GATEWAY_ENABLED=true`: the Durable Object connects to the Gateway to keep the bot online; messages are still sent via REST.
 
-### Bot Command (`!gh`)
+### Bot Commands (comment on GitHub as yourself)
 
-When the Gateway is enabled, reply (quote) a bot-issued issue / PR notification and type:
+When the Gateway is enabled, the bot registers native **slash** and **message context-menu** commands per guild on connect. Comments are posted using **your own** linked GitHub account (OAuth), and permission is delegated to GitHub — if GitHub rejects the action (e.g. editing someone else's comment) the bot tells you so. All replies are ephemeral (only you see them).
+
+**1. Link your account** (once):
 
 ```
-!gh <comment text>
+/gh login     → returns an ephemeral link to authorize your GitHub account
+/gh logout    → unlink your GitHub account
 ```
 
-The bot posts the text as a GitHub comment on that issue / PR (authenticated as the GitHub App).
+**2. Add / edit / delete a comment** — two equivalent ways:
 
-**Extra requirements:**
+- **Right-click a notification** (recommended): right-click a bot-issued issue / PR / comment notification → **Apps** → **GitHub: 添加评论 / 编辑评论 / 删除评论**. The target is auto-extracted from the notification embed; no link needed.
+- **Slash command with a link**:
 
-| Item              | How                                                                                       |
-| ----------------- | ----------------------------------------------------------------------------------------- |
-| Gateway enabled   | `DISCORD_GATEWAY_ENABLED=true`                                                            |
-| Privileged intent | Enable **Message Content** in Discord Developer Portal → Bot → Privileged Gateway Intents |
-| Permissions       | **Read Message History** (to read the quoted message) in addition to sending              |
-| GitHub App        | Installed on the repo with **Issues (write)** permission                                  |
+  ```
+  /gh comment add  link:<issue or PR url>          e.g. https://github.com/owner/repo/issues/123
+  /gh comment edit link:<comment url>              url must contain #issuecomment-<id>
+  /gh comment del  link:<comment url>              url must contain #issuecomment-<id>
+  ```
+
+  For `edit` / `del`, copy the specific comment link on GitHub (comment ⋯ menu → **Copy link**). `add` / `edit` open a modal to enter/adjust the comment body (prefilled for edit).
+
+**Requirements:**
+
+| Item            | How                                                                   |
+| --------------- | --------------------------------------------------------------------- |
+| Gateway enabled | `DISCORD_GATEWAY_ENABLED=true` (interactions arrive over the Gateway) |
+| Invite scope    | Bot invited with `applications.commands` (see invite URL above)       |
+| OAuth           | `GITHUB_CLIENT_ID` / `GITHUB_CLIENT_SECRET` and `BASE_URL` configured |
+| User linked     | Each user runs `/gh login` first                                      |
 
 ## Deployment