Add SSH Console Ownership Boundary (Phase 8D.4)

Implement transport-qualified session identity and immutable owner
adapters
for SSH console lifecycle and output-drain operations. Add focused host
tests
covering admission, stale identities, deferred actions, completion
races,
prompts, backpressure, and slot reuse. Update Phase 8D documentation and
current-state tracking.

docs/phase8d_plan.md

@@ -1,6 +1,6 @@
 # Phase 8D — Incremental web administration plan
 
-Status: **8D.0–8D.2 validated by user sign-off on 2026-09-05; 8D.3/M1 validated by explicit user sign-off on 2026-09-06 after post-soak evidence. Live login/logout is implemented, host-tested and build-verified. Numeric reserve gates remain open. 8D.4–8D.22 remain planned, each requiring a separate implementation request.** See the [8D.3 implementation record](phase8d3_implementation.md) and [8D.0 baseline/M1 contract](phase8d_baseline.md).
+Status: **8D.0–8D.2 validated by user sign-off on 2026-09-05; 8D.3/M1 validated by explicit user sign-off on 2026-09-06 after post-soak evidence. Live login/logout is implemented, host-tested and build-verified. 8D.4 is implemented, host-tested and build-verified; target regression remains pending. Numeric reserve gates remain open. 8D.5–8D.22 remain planned, each requiring a separate implementation request.** See the [8D.4 implementation record](phase8d4_implementation.md), [8D.3 implementation record](phase8d3_implementation.md) and [8D.0 baseline/M1 contract](phase8d_baseline.md).
 
 This is the execution plan for [roadmap Phase 8D](roadmap.md#phase-8--role-based-users-and-administrative-access). The roadmap retains the feature/security requirements; this document defines small work units, dependencies, and release gates. The [administration test matrix](user_administration_tests.md#planned-phase-8d-integrated-web-administration) remains the final acceptance checklist.
 
@@ -102,6 +102,8 @@ If 8D.3 exceeds the work-unit limit, first split out inert login-page rendering
 
 ### 8D.4 — Small transport-neutral console boundary
 
+**Implementation checkpoint (2026-09-06):** [8D.4 implementation, resource accounting and target handoff](phase8d4_implementation.md). Implemented / host-tested / build-verified; target regression pending. Owner callbacks and transport-qualified identity retain the existing two shared slots and SSH API, with no browser routes. Build **95,084 B RAM / 1,627,173 B flash**, **-424 / +1,448 B** versus recorded latest 8D.3. Numeric reserves remain open. This supersedes the overview's older planned status for 8D.4 only; stop before 8D.5 pending validation or explicit user decision.
+
 **Start in:** `src/admin_ssh_console.{c,h}`, `src/console_input.{c,h}`, and only the necessary `src/ssh_transport.c` callers.
 
 **Scope:** Introduce the minimal transport identity/output/lifecycle boundary needed by a future web frontend. Retain the single dispatcher, fixed queue, line editing/history/completion/prompts, currentness checks, generation tokens, and existing SSH API compatibility where practical. Do not duplicate per-SSH buffers for hypothetical web capacity or rename the whole module. No web endpoint or second dispatcher/task.
@@ -167,7 +169,7 @@ Update the roadmap and user/command documentation to distinguish completed featu
 
 ## Progress and next-request template
 
-Progress: **8D.0–8D.3 and M1 validated by user sign-off. 8D.3 implemented / host-tested / build-verified; numeric reserves remain open. 8D.4–8D.22 planned.** Record incremental results in `docs/agent/current-state.md`, retaining the [baseline](phase8d_baseline.md) and cumulative resource measurements as work proceeds. The baseline records user-provided evidence and sign-off; this does not imply completion of later browser-authentication acceptance checks.
+Progress: **8D.0–8D.3 and M1 validated by user sign-off. 8D.4 implemented / host-tested / build-verified, target regression pending; numeric reserves remain open. 8D.5–8D.22 planned.** Record incremental results in `docs/agent/current-state.md`, retaining the [baseline](phase8d_baseline.md) and cumulative resource measurements as work proceeds. The baseline records user-provided evidence and sign-off; this does not imply completion of later browser-authentication acceptance checks.
 
 Suggested next request: