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/agent/current-state.md

@@ -4,6 +4,8 @@ This file is working memory. Update it during active work and before handoff; do
 
 ## Development state
 
+- **8D.4 implemented / host-tested / build-verified (2026-09-06), target pending:** User separately requested the small console boundary. Added transport-qualified identity and immutable output-drain/lifecycle owner callbacks in `admin_ssh_console`, retained the SSH admission API in `ssh_transport`, and kept two shared slots, one dispatcher and all capacities/stacks. Shared completion scratch now has nonblocking ownership; occupied-slot replacement and deferred input fail closed. `python3 tests/admin_console_boundary/run.py` and existing policy suite pass; independent review found no defects. `pio run` passes in **43.61 s**, **95,084 B RAM / 1,627,173 B flash** (**-424 / +1,448 B** versus recorded latest 8D.3). See `docs/phase8d4_implementation.md` for contracts, host-test limits, accounting and target checklist. No browser admin routes, uploads or 8D.5 work. Prior M1 sign-off stands; numeric reserves and 8D.4 target regression remain pending. Stop for validation/user decision before separately requested 8D.5.
+
 - **8D.3/M1 completed by explicit user sign-off (2026-09-06):** User closes M1 after post-soak evidence, superseding all older pending/blocked/in-progress statements below. Four broker clients remain active at 115200 baud (SSH writer; USB/two web observers), both SSH routes and two cookie sessions active. Post-soak internal/DMA/PSRAM free **38,656 / 30,900 / 8,138,320 B**, minima **13,756 / 6,000 / 8,072,744 B**, largest **25,600 / 25,600 / 7,995,392 B**; SSH stack minimum-free **16,288 B**. Minima/largest unchanged from earlier loaded sample; no reported transport failures. Record/evidence limits in `docs/phase8d3_implementation.md`. Sample is still connected, not disconnected cleanup; exact soak duration/revision not supplied. Unrecorded detailed checks do not reopen signed-off M1 or become claims of execution. Numeric reserves remain open; empty-Enter fix target retest remains unrecorded separately. **Wait for a separate 8D.4 request; no M2 implementation performed.**
 
 - **8D.3 both-role target login confirmed / mixed-client evidence (2026-09-05):** User reports successful HTTPS user+admin login after Origin fix; previous login blocker is resolved. Settled internal/DMA/PSRAM free **71,204 / 63,448 / 8,247,744 B**. Mixed load free **33,868 / 26,112 / 8,089,060 B**, minima **13,756 / 6,000 / 8,072,744 B**, largest **25,600 / 25,600 / 7,995,392 B**; SSH stack minimum-free **16,288 B**. 115200 baud, four broker clients (SSH sole writer, USB + two web observers), user/admin SSH active. No reported web transport or SSH I/O errors; 6 login attempts/3 invalid credentials/1 logout, zero security rejections. Two identical loaded heap samples are not a soak/leak or reserve proof. Full details/provenance in `docs/phase8d3_implementation.md`. **M1 validation in progress, not signed off.**