bubo v0.8.7

bubo 0.8.7

This release makes lessons teach instead of giving answers away, flips
bilingual replies so Portuguese comes first, and lets the mascot announce
updates in its own voice.

What's new

• bubo announces updates: when a newer version is available and bubo is
  idle, it opens a speech bubble with the version and the install and later
  actions, instead of leaving the news only in the bottom banner.
• Beginner replies stay on topic: bubo answers what the learner actually
  sent before offering to teach related words or keep talking, instead of
  switching to an unrelated drill.
• Lessons with a second chance: the first miss shows a hint without the
  answer; the second miss (or a reveal) shows the answer with a longer
  explanation and a sad bubo. A correct answer shows a proud bubo.
• No more answers in the examples: lesson bodies and examples were
  rewritten so they illustrate the rule without containing the full exercise
  answer.
• Lessons through B2: present perfect, conditionals and passive voice join
  the catalog, and the lessons entry point is available at every level.
• Portuguese-first bilingual replies: in English + Portuguese mode bubo
  writes Portuguese first and keeps the English behind a "ver em inglês"
  button in the full, compact and popup views.

Upgrade

Nothing to do. Settings → Atualizações offers 0.8.7 like any other version.

Build

• Version 0.8.7, build 1.
• x64 installer signed with the updater key (not Authenticode); SmartScreen may
  warn on first run.
• Update packages are verified with the Tauri updater signing key.

Verification

• 102 Vitest tests, 79 Rust tests, 36 Playwright tests, clippy, fmt, and build
  clean, locally and in CI.