docs(arch): human-mirror-rules + engineering-v1-acceptance, sprint complete

Session 4 of the four-session plan. Final two engineering planning
docs, plus master-plan-status.md updated to reflect that the
engineering layer planning sprint is now complete.

docs/architecture/human-mirror-rules.md
---------------------------------------
The Layer 3 derived markdown view spec:

- The non-negotiable rule: the Mirror is read-only from the
  human's perspective; edits go to the canonical home and the
  Mirror picks them up on regeneration
- 3 V1 template families: Project Overview, Decision Log,
  Subsystem Detail
- Explicit V1 exclusions: per-component pages, per-decision
  pages, cross-project rollups, time-series pages, diff pages,
  conflict queue render, per-memory pages
- Mirror files live in /srv/storage/atocore/data/mirror/ NOT in
  the source vault (sources stay read-only per the operating
  model)
- 3 regeneration triggers: explicit POST, debounced async on
  entity write, daily scheduled refresh
- "Do not edit" header banner with checksum so unchanged inputs
  skip work
- Conflicts and project_state overrides surface inline so the
  trust hierarchy is visible in the human reading experience
- Templates checked in under templates/mirror/, edited via PR
- Deterministic output is a V1 requirement so future Mirror
  diffing works without rework
- Open questions for V1: debounce window, scheduler integration,
  template testing approach, directory listing endpoint, empty
  state rendering

docs/architecture/engineering-v1-acceptance.md
----------------------------------------------
The measurable done definition:

- Single-sentence definition: V1 is done when every v1-required
  query in engineering-query-catalog.md returns a correct result
  for one chosen test project, the Human Mirror renders a
  coherent overview, and a real KB-CAD or KB-FEM export round-
  trips through ingest -> review queue -> active entity without
  violating any conflict or trust invariant
- 23 acceptance criteria across 4 categories:
  * Functional (8): entity store, all 20 v1-required queries,
    tool ingest endpoints, candidate review queue, conflict
    detection, Human Mirror, memory-to-entity graduation,
    complete provenance chain
  * Quality (6): existing tests pass, V1 has its own coverage,
    conflict invariants enforced, trust hierarchy enforced,
    Mirror reproducible via golden file, killer correctness
    queries pass against representative data
  * Operational (5): safe migration, backup/restore drill,
    performance bounds, no new manual ops burden, Phase 9 not
    regressed
  * Documentation (4): per-entity-type spec docs, KB schema docs,
    V1 release notes, master-plan-status updated
- Explicit negative list of things V1 does NOT need to do:
  no LLM extractor, no auto-promotion, no write-back, no
  multi-user, no real-time UI, no cross-project rollups,
  no time-travel, no nightly conflict sweep, no incremental
  Chroma, no retention cleanup, no encryption, no off-Dalidou
  backup target
- Recommended implementation order: F-1 -> F-8 in sequence,
  with the graduation flow (F-7) saved for last as the most
  cross-cutting change
- Anticipated friction points called out in advance:
  graduation cross-cuts memory module, Mirror determinism trap,
  conflict detector subtle correctness, provenance backfill
  for graduated entities

master-plan-status.md updated
-----------------------------
- Engineering Layer Planning Sprint section now marked complete
  with all 8 architecture docs listed
- Note that the next concrete step is the V1 implementation
  sprint following engineering-v1-acceptance.md as its checklist

Pure doc work. No code, no schema, no behavior changes.

After this commit, the engineering planning sprint is fully done
(8/8 docs) and Phase 9 is fully complete (Commits A/B/C all
shipped, validated, and pushed). AtoCore is ready for either
the engineering V1 implementation sprint OR a pause for real-
world Phase 9 usage, depending on which the user prefers next.

docs/master-plan-status.md

@@ -44,8 +44,9 @@ read-only additive mode.
 
 ### Engineering Layer Planning Sprint
 
-The engineering layer is intentionally in planning, not implementation.
-The architecture docs below are the current state of that planning:
+**Status: complete.** All 8 architecture docs are drafted. The
+engineering layer is now ready for V1 implementation against the
+active project set.
 
 - [engineering-query-catalog.md](architecture/engineering-query-catalog.md) —
   the 20 v1-required queries the engineering layer must answer
@@ -55,17 +56,21 @@ The architecture docs below are the current state of that planning:
   Layer 0 → Layer 2 pipeline, triggers, review queue mechanics
 - [conflict-model.md](architecture/conflict-model.md) —
   detection, representation, and resolution of contradictory facts
+- [tool-handoff-boundaries.md](architecture/tool-handoff-boundaries.md) —
+  KB-CAD / KB-FEM one-way mirror stance, ingest endpoints, drift handling
+- [representation-authority.md](architecture/representation-authority.md) —
+  canonical home matrix across PKM / KB / repos / AtoCore for 22 fact kinds
+- [human-mirror-rules.md](architecture/human-mirror-rules.md) —
+  templates, regeneration triggers, edit flow, "do not edit" enforcement
+- [engineering-v1-acceptance.md](architecture/engineering-v1-acceptance.md) —
+  measurable done definition with 23 acceptance criteria
 - [engineering-knowledge-hybrid-architecture.md](architecture/engineering-knowledge-hybrid-architecture.md) —
   the 5-layer model (from the previous planning wave)
 - [engineering-ontology-v1.md](architecture/engineering-ontology-v1.md) —
   the initial V1 object and relationship inventory (previous wave)
 
-Still to draft before engineering-layer implementation begins:
-
-- tool-handoff-boundaries.md (KB-CAD / KB-FEM read vs write)
-- human-mirror-rules.md (templates, triggers, edit flow)
-- representation-authority.md (PKM / KB / repo / AtoCore canonical home matrix)
-- engineering-v1-acceptance.md (done definition)
+The next concrete next step is the V1 implementation sprint, which
+should follow engineering-v1-acceptance.md as its checklist.
 
 ## What Is Real Today