v0.4.0 — delivery contract and safe resumption

A contract and resumption release. Quizzing now only advertises adapters it actually has,
tells you when a saved draft cannot be restored intact, and ships one worked example that
demonstrates every question type rather than a handful.

Changed

• deliveryMethod in answers.schema.json is narrowed to html and local-server.
  The markdown and tui values were removed: neither adapter was ever built, so the
  schema was advertising a contract nothing could satisfy. A consumer that branches on
  those values will no longer receive them. delivery.adapters and delivery.selected in
  questionnaire.schema.json are narrowed to match. This is the reason for the minor bump.
• A browser is now a stated prerequisite rather than something the skill tries to work
  around. Every host CLI is an npm application, so Node is present by construction; the
  browser is the real variable, and Quizzing is human-in-the-loop by definition. The
  conversational fallback in SKILL.md, which guarded an impossible no-Node case, is gone.
• The example corpus is a single questionnaire, file-uploads, replacing
  project-sharing. It is broad enough that every question type is the natural way to ask
  something in it, and it covers both declarative diagram formats, all three required
  modes, and branching. A test now fails the build if a question type or diagram format has
  no example using it.

Added

• A resumed draft now discloses what it could not restore. Drafts carry a fingerprint of
  the question set, so a questionnaire edited without a version bump is detected: the resume
  notice reports how many answers were dropped instead of silently losing them.
• Drafts stranded by a version bump are surfaced with a discard control. Previously they
  sat in localStorage forever, invisible and unreachable.
• recommended.booleanValue is now valid in questionnaire.schema.json, so boolean
  questions can carry a seeded recommendation.
• Four new documentation screenshots covering multi-select, boolean, free text, and ranking.

Fixed

• Connected mode mislabelled its output. buildAnswers defaulted deliveryMethod to
  html and no call site ever passed anything else, so every answers file written by
  serve.js since v0.1.0 claimed to be a static submission. It now reports local-server.
  Found by the test asserting every advertised enum value is emitted by something.
• Boolean recommendations were unreachable. app.js read rec.booleanValue, but
  recommended is additionalProperties: false and never declared it, so the schema
  rejected the only spelling the form understood. Dead since boolean questions shipped.
• Edge labels on predominantly vertical diagram edges no longer have the arrow drawn
  through them.
• Five documentation screenshots were cropped mid-content; viewport heights are now the
  measured content height of each screen.