PyWeb 0.4.0

Apps that are bigger, livelier and smarter: npm packages without
Node.js, multi-page apps with layouts and client-side navigation,
streaming for AI features, and page data that follows the database.

Added

• npm packages without Node.js. pyweb add chart.js/auto downloads a
  package from the npm registry, checks its sha512 checksum, follows its
  imports from the browser entry point and copies only the files it
  needs (and its dependencies) into static/vendor/, pinning versions in
  pyweb.lock. pyweb add with no arguments reinstalls from the lock;
  pyweb remove takes a package out. Browser code binds exports with
  Chart = npm("chart.js/auto") or npm("pkg", "Export"). Calling a
  class constructs it and keyword arguments become an options object.
  Each page imports only the packages it uses, through an import map
  that the Content Security Policy allows by hash. CommonJS-only and
  Node.js-only packages are refused with an explanation, and an
  uninstalled package is a compile error that names the command to run.
• ref={el} sets a page variable to an element, in time for
  on_mount, for libraries that draw into the page.
• Changing an attribute of a package's object (chart.value = 5)
  re-renders whatever shows it.
• Web components (custom elements from npm) work in markup.
• pyweb lsp: hover shows an npm binding's installed version and
  TypeScript signature; completion offers installed packages in
  npm(" and a module's exports after name..
• New docs page: npm packages.
• Layouts. @app.layout wraps every page (or, with
  @app.layout("/admin"), pages under a prefix) in shared markup;
  {children} marks where the page goes. Layouts nest, have their own
  server code, state and handlers, and pages can opt out with
  layout=None or pick one with layout="Name".
• Client-side navigation. Links between pages fetch the next page's
  HTML and swap it in below the layouts both pages share, so layout
  state (an open menu, a player) survives. Links are prefetched on
  hover or focus, back/forward restore the scroll position, and anything
  unusual falls back to a full page load. navigate("/path") from
  pyweb.browser does the same from browser code; on_unmount runs
  when a page is left; App(client_nav=False) turns it off.
• Current links. Links to the current page get
  aria-current="page" and links to its parent sections
  aria-current="true", on the server and after each navigation.
• Head tags. @app.page(description=..., image=..., noindex=...) and
  head(title=..., description=...) in page code add description, Open
  Graph and Twitter tags; App(base_url=...) adds canonical URLs and
  absolute image links.
• Error pages in .pyweb. @app.error(404) / @app.error(500) pages
  take path, status, message or request_id and use root layouts.
• Typed query parameters. Page parameters that aren't in the route
  are read from the query string and converted by annotation (int,
  float, bool, list[...]); bad or missing values answer 400.
• New docs page: Layouts & navigation.
• Streaming server functions. A @server function that yields
  sends each value as it's produced (NDJSON over the same RPC endpoint);
  browser code reads it with async for. stream.cancel() or leaving the
  loop aborts the request and closes the generator on the server, so an
  upstream AI call stops too. Errors raised part-way arrive as
  RPCError. Works with async def generators, under pyweb serve,
  pyweb dev and ASGI, and TestClient.rpc returns the streamed values.
• <Markdown text={...} /> (from pyweb) renders Markdown to safe
  HTML on the server and updates it in the browser as the text changes,
  with the same rules in both places. Raw HTML is shown as text and
  links only accept http(s), mailto and relative URLs.
• ai-chat template and example: a streaming chat with Stop and
  Markdown replies that talks to Anthropic, any OpenAI-compatible server
  (OpenAI, Ollama, vLLM, ...) or a built-in demo model, chosen by
  environment variables. pyweb new NAME --template ai-chat.
• New docs page: Building AI apps.
• Live data. rows = live(db, "select ...", params) in a page or
  layout renders the rows and keeps them current: writes through
  pyweb.db (and pyweb.models) announce their table after commit, each
  distinct query re-runs once per change (bursts coalesced) and sends
  rows to every page showing it only when they changed. Pages follow a
  signed feed; db.notify("table") covers writes made elsewhere. With
  RedisBus it works across processes, and any process can take over a
  query from the page's signed description.
• New docs page: Live data.
• watch(lambda: value, handler) (from pyweb.browser) runs a
  handler whenever a value changes, for work outside markup such as
  redrawing a chart or saving a draft.
• pyweb add applies packages' browser field (browser versions of
  files, modules turned off), so packages such as ethers install.
• New examples: dashboard (live queries and a Chart.js chart from
  npm), site (layouts, navigation, query parameters, a 404 page) and
  ai-chat. The playground has the site and AI chat examples.
• New docs page: Recipe: wallets & web3 (wallet sign-in with ethers and
  eth-account).
• A layout's {children} can sit on a line of its own.

Fixed

• Subscriptions and cleanups set up in on_mount now end when the page
  is left (they were never stopped).

Changed

• The experimental pyweb.live module (in-memory live tables) is now
  pyweb.livetable; pyweb.live is the new live-query function.
• pyweb.npm (TypeScript declarations to dataclasses) is now
  pyweb.dts, and its command is pyweb dts. pyweb build no longer
  writes an esm.sh import map; packages come from pyweb.lock.
• The default Content Security Policy adds worker-src 'self' blob: so
  packages can start Web Workers.
• The starter stylesheet styles Markdown and chat bubbles.
• The browser runtime is about 14 KB gzipped (was about 11 KB), for
  client-side navigation and npm support.
• New website design: a colour system where blue means the browser and
  amber the server, self-hosted Inter / Bricolage Grotesque / JetBrains
  Mono, dark code windows, and a landing page that shows each line of an
  app with where it runs (worked out by the compiler) next to the real
  compiled output.
• The example apps and the pyweb new stylesheet use the new palette.