T24e: Agent, environment

- SandboxStatus: a dot and a word (a ring while it starts or works), what it
  uses of what it has as meters, and how long it has run; the header wraps
- McpServerList over lists::ListItem: a dot per state, what it runs or why it
  failed, its tools once connected, and a switch
- ToolRegistry: tools grouped by source, found by every word of the owner's
  query, each Allow, Ask or Deny; rows wrap at 280px
- MemoryPanel: a line to keep a memory, Enter or Remember, blank words kept
  out; each memory with its source, when, and Forget
- CheckpointList over data_display::Timeline, newest first, the current point
  marked, Rewind on the rest
- gallery: every control wired to state

tasks/ch21-30.md

@@ -193,11 +193,11 @@
 
 ## T24e Agent · Environment
 
-- [ ] SandboxStatus
-- [ ] MCPServerList / ConnectorList
-- [ ] ToolRegistry Panel
-- [ ] MemoryPanel
-- [ ] CheckpointList / Rewind
+- [x] SandboxStatus
+- [x] MCPServerList / ConnectorList → `agent::McpServerList`
+- [x] ToolRegistry Panel → `agent::ToolRegistry`
+- [x] MemoryPanel
+- [x] CheckpointList / Rewind → `agent::CheckpointList`, Rewind on each point but the current
 
 ## T24f Agent · Control and cost