docs: the chat window, the Inbox and security groups

Three of the surfaces a user asks about most had nothing in `docs/`, so the
assistant answered from guesswork: the chat itself (its two layouts, the tab
bar and what lands on which tab, every control around the composer, the slash
commands it must never forward to the model), the Inbox (why background work
asks there rather than in the chat, and that an unanswered card is a stopped
job, not a slow one), and security groups — the honest answer to "why does it
keep asking me for permission?", including what a group is *not*: not a mode,
not a data boundary, and not advisory.

Each page states the misreadings users actually arrive with, since correcting
those is most of the work; the tables list what the person is looking at, not
what the code does.

docs/index.md

@@ -4,12 +4,15 @@ This folder is written for **you, the assistant**, not for the human directly. I
 
 Keep answers grounded in what's actually enabled and configured for this instance — check with the relevant tool (e.g. list installed/enabled plugins) rather than assuming everything described here is turned on. A feature documented here may not be enabled on this particular instance.
 
-This index will grow over time. Right now it covers the interface, view context, files, agents, memory, projects, shared folders, background tasks, system agents, access grants, connectors, skills, the sandbox, voice input and plugins; more sections (security groups…) will be added later.
+This index will grow over time. Right now it covers the chat window, the inbox, the interface, view context, files, agents, memory, projects, shared folders, background tasks, system agents, access grants, security groups, connectors, skills, the sandbox, voice input and plugins; more sections (the mobile app, the admin's Users and Roles pages, the Tasks page, models and providers…) will be added later.
 
 ## Features
 
 | Document | What it covers |
 | --- | --- |
+| [chat.md](chat.md) | The chat window: full-page vs docked, the tab bar and what lands where, the composer's controls, the slash commands, and what happens while an answer is being written |
+| [inbox.md](inbox.md) | The Inbox: the three kinds of pending request, why background work asks here rather than in the chat, answering one (and the time-limited approvals), and why an unanswered card means a stopped job |
+| [security-groups.md](security-groups.md) | Security groups: allow / ask / deny per tool, the shield in the chat, what the default group already permits, and how an admin edits the rules |
 | [memory.md](memory.md) | Private and shared memory: what goes where, the indexes and history log, why some shared facts can't be changed on request |
 | [agents.md](agents.md) | Agents: the three kinds (chat, task, system), which one you are talking to and why, the specialist agents the assistant delegates to, how the model is chosen, and adding a custom agent |
 | [files.md](files.md) | The Files page: everywhere a member can reach — home, both memory stores, shared folders, projects, skills and docs — what they can change there, and what is deliberately read-only |