test: cover untested public API in smoke.mjs (journey + knownThemes)

[ashishbhateja]

What this changes

Adds 5 new assertions to scripts/smoke.mjs, bringing the check count from 19 to 24. Every new check exercises exported API that existed but had no coverage.

journey.js

• monthsOfMovement — the function was not imported or called anywhere in the test suite. New check verifies it returns the five "ground" movement months in calendar order with correct themes.
• movementOf(arc, number) — the existing test only called movementOf with a month object; the alternate branch that takes a raw number and calls monthByNumber internally was never reached. New check exercises it with August (presence) and September (forward).
• mirrorOf reverse lookup — both January and December carry an explicit mirrors field in the real arc, so the reverse-lookup branch (arc.months.find(m => m.mirrors === number)) was unreachable in every existing test. New check builds a minimal synthetic arc where only one side declares the link, forcing that branch.
• mirrorOf null return — no assertion confirmed that months with no mirror partner (May, July) return null.

personalize.js

• Personalizer.knownThemes() — public method exported and documented, zero coverage. New check confirms it returns the union of declared interests and implicit affinity built from reading history, and excludes unseen themes.

Why

These are real code paths that ship in every build. A bug in any of them (e.g. a refactor that accidentally breaks monthsOfMovement's sort, or the mirrorOf reverse-lookup path) would go undetected. The coverage gap was the only reason to open this PR.

Checklist

• node scripts/smoke.mjs passes (24 checks)
• No new runtime dependencies
• No UI changes
• No magazine content committed (developed against the sample edition)

---

Generated by Claude Code