v0.5.0 — Consistency checks

A coherence release. Quizzing asks one question at a time, which until now meant nothing
noticed when two answers contradicted each other — the incoherent design reached the agent
intact. The form now checks answers against one another, explains what is wrong, and offers
to fix it.

Added

• Cross-question consistency checks. A questionnaire may declare a top-level
  consistency array. Each check fires when every rule in its when array holds, using the
  same condition shape as branching (questionId with equals, includes, gte, or
  lte) — no new operators were introduced. This closes FR-053, FR-054, and FR-055.
• Two severities, because blocking is not always right. An error stops the Next button
  on the question that created the conflict, so the problem is raised while the user is
  still thinking about it. A warning is explained at the review screen, does not block, and
  can be accepted deliberately. A detector that only ever hard-blocks becomes a trap the
  moment a check is subtly wrong.
• One-click corrections. A check may suggest fixes, each a button that sets named
  answer fields. A correction only sets what it names and never clears anything else.
• Checks explain themselves. explain says why the combination is a problem and
  evidence carries the environmental facts behind it — the place where a fact discovered
  during the bearing phase does visible work.
• validation.warnings and validation.checks in answers.schema.json. Every firing
  check is recorded with its severity, and an accepted warning carries acknowledged: true,
  so an agent can tell a considered trade-off from an oversight. validation.status becomes
  partial when only warnings are present. This is additive: issues and status keep
  their existing meaning and shape.
• The bundled file-uploads example declares three checks, including a contradiction
  that was already latent in it, and its answers artifact now shows an accepted trade-off
  rather than an empty validation block.

Fixed

• Roadmap ledger accuracy. TASK-125 (questionnaire versioning and safe resumption) was
  still described as missing detection and disclosure, which is precisely what v0.4.0
  shipped. It is now marked delivered at v0.4.0, along with its TEST-104.