docs: 1.0 documentation restructure

Split root CLAUDE.md into 19 per-directory files scoped to their source area.
Roll v0 history into docs/ARCHIVE.md; retire CONTEXT.md, CONTEXT-ARCHIVE.md,
PLAN.md, COMPLETED.md. Move plan docs under docs/. Rescue 9 live deferrals
into docs/TODO.md.

src/core/audio/CLAUDE.md

@@ -0,0 +1,13 @@
+# src/core/audio — pure audio-data math
+
+## Scope
+
+Pure, REAPER-free audio-data math with no dependence on REAPER's own peak-cache
+API. Currently one module: waveform min/max bin computation from raw PCM. Does
+**not** include: LICE waveform drawing (`draw_kit`, `shell/panel`), the editor's
+waveform/marker geometry (`waveform_view`, `core/instrument/ui`), or PCM
+decoding itself.
+
+## Modules
+
+- `peaks` — waveform min/max bin computation from raw PCM; does not depend on REAPER's peak API.