Copy: pare product claims to what we can certify, cut rule-of-three cadence, record arch 10 §10

README.md

@@ -2,7 +2,7 @@
 
 A browser-based **snippet manager for [Vega-Lite](https://vega.github.io/vega-lite/)
 visualizations**. Author chart specs as JSON, watch them render live, and keep a personal,
-searchable library — fully local, offline-capable, no account.
+searchable library — local, offline-capable, no account.
 
 > Astrolabe is a **spec-driven rebuild** on an architecture adapted from its sibling
 > project Syto. The authoritative behavioral contract lives in [`docs/spec/`](docs/spec/).
@@ -23,10 +23,28 @@ npm run typecheck
 npm test           # Vitest
 ```
 
+## What it does
+
+- **Editor + live preview** — write Vega-Lite specs as JSON in Monaco with schema-aware
+  validation and autocomplete; the chart re-renders as you type.
+- **Snippet library** — save, search, tag, and organize specs. Each snippet carries a stable
+  published version plus a separate editable draft, so you can tinker without losing a
+  known-good copy.
+- **Reusable datasets** — store data once (inline, or fetched once from a URL and snapshotted)
+  and reference it by name from many snippets.
+- **Chart Builder** — a no-JSON on-ramp that generates a spec from field, mark, and encoding
+  choices. The JSON stays the source of truth and is always editable.
+- **Theming & fonts** — custom chart themes with a visual Theme Builder, a curated font roster,
+  and your own uploaded font faces.
+- **Local-first** — your library lives in the browser (IndexedDB); offline-capable and installable
+  (PWA), with import/export for backup and transfer. No account, no server.
+
 ## Status
 
-**M0 — Skeleton.** Toolchain green (typecheck, tests, build, PWA). The three-pane shell
-renders; features land milestone by milestone per the implementation plan (MVP at end of M1).
+Active development, **pre-1.0** and not yet publicly released — well past the initial milestones
+and usable day to day; the first public release will be `1.0.0`. Behavior is specified in
+[`docs/spec/`](docs/spec/) and the architecture patterns in
+[`docs/architecture/`](docs/architecture/00-overview.md).
 
 ## License