potluck: README sells and gets to TADA; CONTRIBUTING has the rest

The README was EmDash's template blurb. Now it says what potluck is
and its first block runs from a fresh clone to /issues, using a new
`pnpm seed:issues` script that applies seed/issues.json to the local
D1 database. CONTRIBUTING covers how it's put together, seeds, checks,
the EmDash rules, and deploying; the template's stale notes (Inter,
three-column articles) are gone. AGENTS.md is now a symlink to it.

Generated-by: Claude Opus 5.5

potluck/package.json

@@ -9,6 +9,7 @@
   },
   "scripts": {
     "dev": "astro dev",
+    "seed:issues": "emdash seed seed/issues.json -d \"$(find .wrangler/state/v3/d1 -name '*.sqlite' ! -name metadata.sqlite)\"",
     "build": "astro build",
     "preview": "astro preview",
     "deploy": "astro build && wrangler deploy",
@@ -29,4 +30,4 @@
     "wrangler": "^4.125.0"
   },
   "packageManager": "pnpm@11.9.0+sha512.bd682d5d03fe525ef7c9fd6780c6884d1e756ac4c9c9fe00c538782824310dcf90e3ddc4f53835f06dfaebd5085e41855e0bcbb3b60de2ac5bbab89e5036f03b"
-}
+}