Rename "In progress" filter to "Open" and add a new "In progress" bucket

[dfuchss]

What

The paper-list annotation filter previously offered In progress for every
unfinished paper. This renames that bucket to Open and adds a new, narrower
In progress bucket for papers that have actually been started — at least
one annotation entry recorded, still not marked finished.

Filter order is now: All · Open · In progress · Finished · With issues.

Why

"Open" (everything not signed off) and "started but not finished" are two
distinct questions. Reviewers wanted to see the work they've actually begun,
separately from papers they haven't touched yet.

Notes

• In progress is the started subset of Open — decided from whether the
  seat has recorded any annotation (touched), not from the dot state. A paper
  whose only entry is a Yes/No answer counts as started even though its dot still
  reads empty (completeness ignores booleans).
• matchesFilter gained a touched argument (defaults to false; only
  In progress consults it).
• Changes: src/model/annotationState.ts, src/components/PaperList.tsx,
  tests in src/components/PaperList.finished.test.ts, and docs
  (README.md, user-guide/getting-started.md).