Learn content: strengthen curriculum upstream (french/spanish/culture-guide) + cloze exercises, then re-export

[OriNachum]

The stories, exercises, and scenarios shown at agentculture.org/learn are
exported from the subject CLIs — the curriculum is authored upstream in
french-cli,
spanish-cli, and
culture-guide, then
learn site export regenerates the site's content. So content improvements
happen upstream first, then re-export here. This is the learn-cli umbrella
tracking issue; per-CLI issues can spawn from it.

Scope

• Deepen + expand each subject's curriculum: more and better stories, richer
  exercises, glossaries, more levels, stronger pedagogy and progression.
• Add a "missing word / pick the right word" (cloze) exercise type to the
  subject-plugin contract + each subject. (This also feeds the per-learner custom
  story generation in the companion experience issue Learn experience: role-based visibility + approved-user LLM tutoring (Bedrock Nova Sonic 2 / Nova Pro) #8.)
• Re-run learn site export and redeploy so /learn reflects the upstream work.

Process

1. Improve content in the upstream CLI (french-cli / spanish-cli / culture-guide).
2. Bump + release the CLI; learn picks up the new content via export.
3. Redeploy the Pages site (agentculture-learn).

Constraints

• Keep the contract's item_id join key stable across edits so learner
  progress/mastery survives content changes.
• Stay contract-conformant: learn subject doctor must stay green for every subject.
• Public export continues to exclude dev-prefixed fixture stories.

Acceptance (rough)

• Each language subject: expanded story ladder + exercise variety including cloze.
• culture-guide: expanded scenarios.
• New content live at /learn after export + deploy, all subject doctors green.

Companion issue: the experience tier (roles/visibility + approved-user LLM
tutoring) is tracked in #8. Build brief: #1.

• learn-cli (Claude)