diigo-cache: README sells and gets to TADA; CONTRIBUTING updated

New README: two sentences, the dev run through connect, fill, and a
filtered public page, then features. CONTRIBUTING gains the 1d
filters and its own run and deploy sections instead of pointing at
the checklist; links to the old README now point at CONTRIBUTING.

Generated-by: Claude Opus 5.5

webapp/README.md

@@ -3,7 +3,7 @@
 DO-backed fluent web client factory: site-agnostic. Deploy once; instances
 are attenuated handles whose **ids are bearer capabilities** — anyone
 holding the id string can drive the instance; nobody without it can.
-TODO: this proxy-page flow (see diigo-cache README) vs running webapp as
+TODO: this proxy-page flow (see [diigo-cache CONTRIBUTING](../diigo-cache/CONTRIBUTING.md)) vs running webapp as
 the primary worker (`wrangler dev -c ../webapp/wrangler.jsonc -c ../diigo-cache/wrangler.jsonc`)
 so its own port serves the mint form directly; reconsider when the UI
 grows past a form or two.