feat: add /context prompt breakdown

docs/tools/slash-commands.md

@@ -55,6 +55,7 @@ Text + native (when enabled):
 - `/help`
 - `/commands`
 - `/status` (show current status; includes a short provider usage/quota line when available)
+- `/context [list|detail|json]` (explain “context”; `detail` shows per-file + per-tool + per-skill + system prompt size)
 - `/usage` (alias: `/status`)
 - `/whoami` (show your sender id; alias: `/id`)
 - `/config show|get|set|unset` (persist config to disk, owner-only; requires `commands.config: true`)
@@ -90,7 +91,9 @@ Notes:
 - `/verbose` is meant for debugging and extra visibility; keep it **off** in normal use.
 - `/reasoning` (and `/verbose`) are risky in group settings: they may reveal internal reasoning or tool output you did not intend to expose. Prefer leaving them off, especially in group chats.
 - **Fast path:** command-only messages from allowlisted senders are handled immediately (bypass queue + model).
-- **Inline shortcuts (allowlisted senders only):** `/help`, `/commands`, `/status` (`/usage`), `/whoami` (`/id`) also work when embedded in text.
+- **Inline shortcuts (allowlisted senders only):** certain commands also work when embedded in a normal message and are stripped before the model sees the remaining text.
+  - Example: `hey /status` triggers a status reply, and the remaining text continues through the normal flow.
+  - Currently: `/help`, `/commands`, `/status` (`/usage`), `/whoami` (`/id`).
 - Unauthorized command-only messages are silently ignored, and inline `/...` tokens are treated as plain text.
 
 ## Usage vs cost (what shows where)