feat(web): state the rules, reach the chat from the top of the board, lint the tree

A /rules page says, in one place, what nothing in the app said before:
the chain rule, the clock, what a dead end costs, elimination and the last
player standing, how a word is scored and the reconnect window. Linked
from the landing page and from the board and lobby headers.

The chat control moves above the chain as a pill with the unread count,
where it can be reached on a phone mid-game, and the lobby's folded chat
now carries an unread badge too.

ESLint with the Svelte and JSDoc plugins, run in CI; the real findings
it turned up (missing each keys, untyped timer handles) are fixed.

web/tests/bundle.test.js

@@ -15,7 +15,6 @@ const srcDir = fileURLToPath(new URL('../src', import.meta.url));
 
 /**
  * Every file in the built output, recursively.
- *
  * @param {string} dir
  * @returns {string[]}
  */
@@ -32,7 +31,6 @@ function walk(dir) {
  * A minifier configured to emit ASCII writes Vietnamese as escapes, and a
  * substring search over the raw bytes would then find nothing while the words
  * are plainly there in the shipped file.
- *
  * @param {string} text
  * @returns {string}
  */