PRISM v2.16.0 — Operating-model backbone

MINOR, additive (no construct renumbering). Slice 2 of the dependency-ordered
sequence: the lanes/Desk backbone the dispatch round-trip (2.17) and closure
(2.18) build on.

Surface

• Lanes / roles operating model (new §3.7). An engagement runs as parallel
  lanes (each = {resume pointer, append-only log, inbox, one concern}) worked
  by sessions in a flexible role × context-tier matrix. Three isolate options
  (inline / separate session / clean-context sub-agent), with the sub-agent the
  default for a clean-context role when the holding session is contaminated
  (self-trigger). The net-helpful bar: the machinery is the session's
  bookkeeping, never the operator's.
• PRISM Desk + PRISM Meta standing-lane constructs, with the operator-facing
  PRISM UI (View+Controller over the repo Model; STATE/HEALTH/ACTION
  surfaces; render-from-verified-model), <Lane>-<N> session numbering, and the
  /prism-meta lane-entry command. Desk discipline: dispatch-not-execute,
  state-correction, propagate-don't-make-the-operator-the-checker, catch-one →
  propose-a-sweep. The stop-set: pause only at real gates (ratify strategy,
  scope change, ratify close, anything sent to the client), else auto-handle and
  report.
• Cross-lane OPEN_ITEMS inbox (§3.7.3) — tier classification (append-only /
  single-writer pointer / canonical), per-writer namespaced IDs, append-only
  dispositions, owner-drain, cross-lane handoffs, and the commit-discipline rule
  (rebase-on-live-tail / commit-only-own / commit-then-confirm). What's next
  splits into the single-writer body + the inbox; resume gains a drain step.
• Bundle-load integrity (§3.7.6) — a phase→bundle manifest in core + a
  per-session fail-loud entry-check + an inbox bundle-miss flag + a Desk
  re-sync audit (the safety net for the v2.19 core-slimming refactor).
• Setup onboarding & quick mode (new §6.6). SETUP_ONBOARDING: Setup
  generates the per-engagement SI from a template (gather → generate → ratify →
  commit → emit project-create/install cards), two-project model.
  SETUP_QUICKMODE: a first-class light mode (one ephemeral session, sub-agent
  fan-out; keeps the mini decision-brief + lite Probe-1 + SP-16/17/18 gates;
  graduation seeds a repo_backed Master).
• M5 self-band — fires per standing session's own context, not only the
  engagement band (Monitor extension, not a new SP).

Calibration / report back

• Does the lane/role model stay invisible to the operator (the net-helpful bar),
  or does it leak machinery into the operator's view?
• Does the OPEN_ITEMS inbox + commit-discipline eliminate the pointer/snapshot
  clobber class in live parallel runs?
• Does the stop-set draw the auto-vs-ask line where the operator wants it?

Provenance. Lens Library unchanged (v0.15). Snapshot PRISM_v2_16_0.md
(byte-identical at the v2.16.0 tag). Reference detail in Appendix I /
reference/lanes-ui.md. Source specs (Engagements clone): LANES_ROLES_PRISM_UI,
OPEN_ITEMS_inbox, SETUP_ONBOARDING, SETUP_QUICKMODE.

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Part of the PRISM v2.15.0 → v2.19.0 promotion arc. See RELEASING.md.