v1.1.0 — MVP 1.1: Adaptive diagnostics + Multi-user sessions

v1.1.0 — MVP 1.1: Adaptive diagnostics + Multi-user sessions

Target branch: main (release back-port merged via admin PR; main is gated by a
repository ruleset requiring PR review + CI, so the back-port was merged as admin).

MVP 1.0 (foundation, Steps 1–6)

• CI hermetic fix — tests/conftest.py pins run_diagnostic=False in the autouse
  offline fixture so a developer .env (RUN_DIAGNOSTIC=true) can't pull the
  diagnostic/interrupt path into offline tests (#70).
• ruff format gate — ruff format --check . now runs in ci.yml; whole tree
  reformatted (#71).

MVP 1.1 — Adaptive diagnostics (Issue #7)

• DiagnosticAgent + adaptive quiz → WeaknessReport; NereusGraph(run_diagnostic=True)
  wires a diagnostic → interrupt → coach entry for weak-area-ordered roadmaps.
• _diagnostic_node resume parsing hardened: a non-JSON/opaque Command(resume=...)
  no longer raises ValueError (dict(received) → {}) + 3 interactive e2e tests (#72).
• Examiner pass threshold difficulty-scaled (70 + difficulty*15, ≤ 85).
• CLI/env: --diagnostic, RUN_DIAGNOSTIC, DIAGNOSTIC_QUESTION_COUNT.

MVP 1.1 — Multi-user sessions (Issues #8 / #57)

• SQLite UserStore + UserSession on-disk persistence (SESSION_ROOT).
• New Redis UserStoreRedis backend (Redis hash per user, degrades to memory) +
  build_user_store() factory dispatching on USER_STORAGE (sqlite/redis/memory) (#69, #73).
• docker-compose.yml: new redis:7 service + USER_STORAGE/REDIS_* env (#73).
• CLI: --new-session, --session-id, --user-id.

Verification

• ruff check . + ruff format --check . — clean
• pytest — 174 passed, 2 skipped (live suites gated by NEREUS_RUN_LIVE=1)

Refs #7, #8, #57.