Rework the README with current screenshots

The README was a bare file list. It now opens with the horizontal
lockup, a theme-aware hero and a workspace dashboard, both taken from
the running app, so GitHub's preview shows the product instead of
describing it.

AGENTS.md records that the design handoff is outdated: its screens and
briefs are history, while its brand assets (stones, coordinator, app
icon, wordmark) and their copies in src/data are still the foundation.

AGENTS.md

@@ -1,6 +1,13 @@
 # Agent Instructions
 
-This is **Cobble** (`cobble.moduletrace.org`): an open-source crew of small AI worker bots. The design handoff in `assets/handoff/` (gitignored locally: `PRODUCT.md`, `IMPLEMENTATION.md`, `tokens/`) is the starting point for the core concepts and visual language, not the end product. The app is expected to move away from it; when it and the current code or the user disagree, the code and the user win. Unit noun is **bot**, never "agent" or "expert".
+This is **Cobble** (`cobble.moduletrace.org`): an open-source crew of small AI worker bots. Unit noun is **bot**, never "agent" or "expert".
+
+**The handoff is outdated.** `assets/handoff/` (gitignored locally: `PRODUCT.md`, `IMPLEMENTATION.md`, `tokens/`, `assets/`) is the *foundation*, not the design: it is what the project started from, and the app has moved well past it. Its layouts, screens (`assets/screens/*.png`), right-hand "working on" panel, and PRODUCT/IMPLEMENTATION briefs describe an early single-chat prototype and must not be used as reference for the current UI or copied into docs, screenshots or marketing. What is still authoritative in it:
+
+- **Brand assets:** the stone icons (`public/brand/icons/*.svg`, mirrored into `src/data/stone-geometry.ts`), the coordinator (`public/brand/coordinator/`), the app icon (`public/brand/app-icon/`), and the wordmark (`public/brand/wordmark/`, mirrored into `src/data/wordmark-paths.ts`). These are the identity and do not change; the mark is a stone with exactly one flat cut, hue is a bot's identity (never status), the coordinator is hue-less.
+- **Tokens:** `tokens/tokens.css` was the origin of the `:root` / `.dark` block in `src/styles/main.css`. From here on `src/styles/main.css` is the source of truth; treat the handoff CSS as historical.
+
+For the current UI, read the code: `src/layouts/bots/` (rail, workspace rail, user popover), `src/pages/admin/bots/[bot_id]/` (conversation header, thread, composer, modals) and `src/pages/admin/workspaces/` (dashboard). When the handoff and the current code or the user disagree, the code and the user win, always.
 
 ## Stack
 
@@ -238,7 +245,7 @@ Server functions use `index.server.ts` alongside `index.tsx` (e.g. `single-docum
 - **UNCHANGEABLE RULE - twui components always win over raw JSX elements.** Use twui components (`H1`-`H5`, `P`, `Span`, `List`, `Img`, `Row`, `Stack`, `Container`, `Section`, `Card`, `Button`, `Tag`, `Link`, etc.) before basic JSX elements (`<h1>`-`<h6>`, `<p>`, `<span>`, `<ul>`, `<li>`, `<img>`, `<a>`, `<button>`, `<div>`-as-card, etc.). Never introduce or reintroduce a raw JSX element where a twui equivalent exists. Override twui defaults via `className` rather than reaching for the raw element.
 - **Never create new CSS classes, CSS files, or inline `style={{...}}` hacks.** Style exclusively by composing existing component props/classNames, existing twui classNames (`twui-*`), semantic theme-token utilities (`bg-dark`, `bg-light`, `text-dark`, `text-primary`, `bg-primary`, `text-accent`, `bg-accent`, `text-secondary`, `border-slate-200`, etc.), and utility classes already used elsewhere in this codebase. Build up from what exists; extend component code only when the existing API cannot express the need.
 - **Theming:** colors, radii, and fonts change only in `src/styles/main.css`: Cobble tokens as CSS vars on `:root` (light) and `.dark`, exposed in the `@theme inline` block as `paper`, `surface`, `sunken`, `ink`, `ink-secondary`, `ink-disabled`, `hairline`, `hairline-strong`, `on-ink`, `hue-<name>`, plus `shadow-popover` and `--m-fast/base/slow` motion vars (zeroed under reduced motion). Font is Lato (stand-in). Never hardcode hex colors, radii, or font stacks inside components. Hues are bot identity only, never state; use `src/dict/bot-hue-classes-dict.ts` for hue classes.
-- **Branding:** `public/logos/logo.svg` is the single source of truth for the logo mark; `logo-icon.tsx` renders it inline (via `BotStone`) and `logo.tsx` renders the stone beside the vector `Wordmark`. Whenever the logo changes, run `bun run gen:favicon` to regenerate `public/favicon.ico`, `public/favicon.png`, `public/apple-touch-icon.png`, and `public/logos/logo.png` (the last is used in emails). Font + favicon links live in `__root.tsx` `Head()`.
+- **Branding:** `docs/readme/hero-light.png`, `hero-dark.png`, `workspace-light.png` and `workspace-dark.png` are screenshots of the current app (chat and workspace dashboard, 1440px at 2x, downscaled to 1600px wide), committed and picked per theme by GitHub's `#gh-light-mode-only` / `#gh-dark-mode-only` fragment. They are not generated: when the UI changes, retake them from a seeded dev instance (`bun run seed`, `bun run seed:bots`) and keep the same names, so the README never shows an older dashboard. Never use `assets/handoff/assets/screens/*.png` for anything: that design is outdated. `public/logos/logo.svg` is the single source of truth for the logo mark; `logo-icon.tsx` renders it inline (via `BotStone`) and `logo.tsx` renders the stone beside the vector `Wordmark`. Whenever the logo changes, run `bun run gen:favicon` to regenerate `public/favicon.ico`, `public/favicon.png`, `public/apple-touch-icon.png`, and `public/logos/logo.png` (the last is used in emails). Font + favicon links live in `__root.tsx` `Head()`.
 - **Site name:** brand literals live only in `src/data/site-data.ts`. Page meta titles, emails, and UI copy must interpolate `SiteData["SiteName"]` - never hardcode a brand name in page files.
 
 ## Conventions