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/json/CLAUDE.md

@@ -0,0 +1,20 @@
+# src/core/json — the hand-rolled JSON lexical layer
+
+## Scope
+
+The ONE hand-rolled JSON lexical layer used across the pure core: string/number/
+bool/null tokens, the scoped object `Writer`, and the bounds-checked `Reader`
+cursor. Domain grammars — what fields a bank, view-mode, or manifest blob actually
+has — stay in the consumers; this module owns lexing/emitting only.
+
+## Modules
+
+- `json` (`core/json`) — the ONE hand-rolled JSON lexical layer (Q-W1): string/number/bool/null tokens, the scoped object `Writer`, and the bounds-checked `Reader` cursor, byte-compatible with the five pre-extraction per-module writers it replaced (`bank_model` / `bank_book` / `view_mode_model` / `owned_manifest` / `tail_control`). Domain grammars stay in the consumers; this owns lexing/emitting only.
+
+## Gotchas
+
+- Byte-compatible with the five pre-extraction per-module writers it replaced
+  (`bank_model` / `bank_book` / `view_mode_model` / `owned_manifest` /
+  `tail_control`) — a change here risks silently breaking round-trip compatibility
+  with ext-state blobs already persisted by projects written before the Q-W1
+  extraction.