P2a: eight-bar arrangement with four editable sections

docs/P2.md

@@ -0,0 +1,27 @@
+# P2 · arrangement, render, agent
+
+P2 turns the loop into a thing that can be played, rendered and performed with an agent. It is delivered in three slices.
+
+## P2a · the arrangement
+
+Four 2-bar sections (A–D) form an 8-bar loop. Each section is a full `Pattern` (5 rows × 16 steps, with per-row faces). The engine walks 64 steps, picks the section and the pattern step, and triggers the section's rows; the bar clock runs 1–8. The state carries `arrangement: [Pattern; 4]`, `active_section`, and `pattern` = the active section for the editors.
+
+Commands: `select_section { index }`, `clear_section { index }`, `copy_section { from, to }`, event `arrangement { sections, active }`. Pattern edits apply to the active section. Select is persisted but not undoable; clear/copy push history. Sections, the active index and their history are stored in SQLite (`arrangement`, `active_section` columns, migrated with `ensure_column`) and restored on load.
+
+Surface: the quarry gets a section strip (A–D with note counts, copy →, clear); the pattern grid edits the active section. The descent draws the 64-step road, bar labels 01–08, section seams and letters A–D, with the active section emphasized; the playhead follows the 8-bar clock.
+
+Verification:
+
+- `cargo test -p zhila-core arrangement`: sections independent, select/copy/clear, undo, material carries four sections, loop_bars = 8.
+- `node scripts/persistence-smoke.mjs`: imports, edits section B, copies A→C, cuts, restarts, verifies the arrangement, active B, B's step 0 = 0, C = A, and undo/redo.
+- `npm --prefix ui run arrangement-smoke`: four sections, select B, edit a step, switch to the nave, play, screenshot `preview-p2-arrangement.png`.
+
+Limits: exactly four sections of two bars; no insert/reorder/length; select is not undoable; no per-section mute.
+
+## P2b · render (next)
+
+Offline render of the 8-bar arrangement to a WAV inside the project, with a command and a surface control.
+
+## P2c · agent (next)
+
+An in-app LLM agent on the same verbs, with state/sound context and approval for project edits.

docs/PLAN.md

@@ -1,7 +1,7 @@
 # ZHILA — план проекта
 
 Черновик v1.1 · 1 ноября 2026
-Статус: **P1 полностью выполнен** (P0, P1a–P1f; см. `P0.md`, `P1.md`). Демо `reference/demo/` — референс, не кодовая база. Следующая фаза — аранжировка, рендер и агент.
+Статус: **P2 в работе** (P0, P1a–P1f, P2a; см. `P0.md`, `P1.md`, `P2.md`). Демо `reference/demo/` — референс, не кодовая база. Осталось: рендер WAV и агент.
 
 **Зафиксировано 1 ноября:** descent — основной вид; камень = паттерн; климат — на жилу (концепт погоды остаётся); платформа v1 — Linux; UI — Svelte 5. Журнал — §9.
 

docs/PROTOCOL.md

@@ -168,3 +168,7 @@ No new wire messages. The daemon now persists the session's bounded `history` an
 ## P1f note
 
 The Tauri app starts the same host in-process, so the wire contract is unchanged. The embedded surface connects to `ws://127.0.0.1:4317` with the same hello, token and origin rules; the daemon remains the browser-development host.
+
+## P2a additions
+
+`State` adds `arrangement: Pattern[]` (four sections in this phase) and `active_section: u8`; `State.pattern` is the active section. Commands `select_section { index }`, `clear_section { index }`, `copy_section { from, to }`; event `arrangement { sections, active }`. Pattern step/face commands edit the active section. The project row stores `arrangement` and `active_section`; old projects with only `pattern` are migrated to four copies of it.