Specify retained terminal presentation

docs/specification.md

@@ -614,6 +614,42 @@ Interactive terminal control requires:
 Disconnected Client Sessions close rather than reattach to an unbounded scrollback
 owned by the coordinator.
 
+#### Retained terminal presentation
+
+The application model owns terminal-route transitions. Their retained-screen
+physical refinement is:
+
+```mermaid
+flowchart LR
+    Guest[Sandbox PTY output]
+    Buffer[Kernel PTY buffering]
+    Screen[HC retained screen]
+    Client[Paired Client terminal]
+    Trusted[Prompt or HostProcess presentation]
+
+    Guest -->|Sandbox route| Screen
+    Screen -->|derived rendering| Client
+    Guest -.->|Prompt or HostProcess route: reads paused| Buffer
+    Trusted --> Client
+    Trusted -->|return to Sandbox| Restore[redraw retained screen]
+    Restore --> Client
+    Buffer -->|resume in byte order| Screen
+```
+
+- The retained screen belongs to the existing fixed Host Coordinator and Client
+  Session pair. Existing Session Terminal cleanup discards it and any partial
+  input-decoder state; another Client cannot attach to or adopt it.
+- Prompt and HostProcess presentation does not mutate the retained sandbox
+  screen. Returning to `Sandbox` restores that screen without guest input,
+  signals, resize, or application redraw.
+- Requester-controlled bytes render inertly with argument boundaries preserved.
+  Approval defaults to denial and uses a bounded, fragmentation-independent
+  escape-sequence interval; incomplete, ambiguous, pre-prompt, interrupted, or
+  lost input cannot approve.
+- The guest terminal profile exposes only qualified parser, renderer,
+  key-translation, and terminal-reply behavior. Replies derive from retained
+  state rather than the physical Client terminal.
+
 The session connection carries the terminal events and messages described by
 this refinement. Interactive sessions negotiate `lazaret-control/2` through
 TLS ALPN before any version-specific record is decoded. A new Client refuses an
@@ -1224,6 +1260,7 @@ not duplicated here.
 | **FR-20** | Physical network readiness shall use product-owned known-live targets. DNS, public egress, and configured destination availability shall not gate it. |
 | **FR-21** | The Domain Store and Storage Catalog shall preserve the independently recoverable ownership, identities, and authority relationships described by the durable-generation and prepared-lower refinements. |
 | **FR-22** | Preparation shall use a supported OCI-aware preparer that materialises a Lazaret-owned immutable rootfs with source identity and prepared-artifact ID. |
+| **FR-23** | Each interactive Client Session shall use the retained-screen refinement defined in **Retained terminal presentation**. |
 
 ### 4.3 Developer-Experience Requirements
 
@@ -1232,7 +1269,7 @@ not duplicated here.
 | **DX-1** | `lazaret <profile>` shall launch the explicitly named Agent Profile in the current workspace and start `/bin/bash` as a new interactive Client Session. A trailing `-- <command> [arguments...]` shall replace that default with the exact supplied argument vector. |
 | **DX-2** | Tools installed in configured persistent sandbox paths and dependencies stored in Ignored Workspace State shall remain available on later launches of the same Domain. |
 | **DX-3** | Normal source editing, `git status`, staging, committing, and reference updates shall work from inside the Agent Sandbox. |
-| **DX-4** | Escalation prompts shall identify the requesting profile, session, command, and justification without mixing terminal input or output between sessions. |
+| **DX-4** | Escalation prompts shall show the requester, command, and justification, with explicit approve and deny actions. |
 | **DX-5** | Failures shall report actionable diagnostics and shall not leave the developer's terminal in a corrupted mode. |
 | **DX-6** | State inspection shall provide human-readable and machine-readable output without exposing persisted file contents by default, and reset shall show its resolved Domain and exact scope before confirmation. |