fix(onboarding): source topic list from DB to stop selections being silently dropped

[nicholasjjlim]

🚀 Summary

Closes #598.

The onboarding topic picker rendered a hardcoded list and submitted display titles, which the POST handler matched case-sensitively against Collection.title. The UI list and DB drifted (Artificial Intelligence vs AI, Educator Voices vs Educators Voices, etc.), so selections silently failed to match — some learners couldn't complete onboarding (400, no profile created), others had picks dropped with no error (200, partial save).

This sources the selectable topics from the database and submits collection ids, so the picker and the validator can never drift again.

✏️ Changes

• (protected)/+layout.server.ts — query topic collections (isTopic = true, selecting id, title, description, tag.code) and expose them as onboardingTopics. Keyed distinctly from the home page's own topics (different shape) — page data overrides layout data on key collision, which would otherwise leave the picker empty.
• (protected)/+layout.svelte — pass onboardingTopics down to OnboardingView.
• OnboardingView.svelte — remove the hardcoded collectionsList; accept a typed topics prop; render from it; submit collection ids. Icons are keyed off the stable tag code (e.g. AI, BOB) — the same identifier Collection.svelte uses — not titles/slugs, so they can't drift. Topics without a known icon are filtered out and not shown.
• api/onboarding/+server.ts — request body changes from topics (titles) to collectionIds (UUIDs). Ids are resolved strictly: if the resolved isTopic = true count ≠ submitted (deduped) count, log a warning and return 422 instead of saving a partial profile. Duplicate ids are deduped so they can't create duplicate UserInterest rows. csrfToken handling and LearningFrequency mapping unchanged.
• api/onboarding/server.test.ts — new tests covering the full success/error contract (401, 415, 400, 422 for invalid body / fewer than 3 / unresolved id, dedup, 500 on DB failure, 200 with one interest per id).

No Prisma schema change or migration.

✅ Verification

• pnpm test run — 350/350 pass (11 new onboarding handler tests).
• pnpm check — 0 errors, 0 warnings.
• Manually verified the picker renders the seeded topics with icons on the home route.

🤖 Generated with Claude Code

[nicholasjjlim]

Code Review Summary

Severity	Count
Critical	0
High	1
Medium	1
Low	2

What Looks Good

• The core fix is correct and complete: topics now flow from the DB and selections are submitted as collection IDs, eliminating the case-sensitive title-matching that silently dropped selections (fix(onboarding): source topic list from DB to stop selections being silently dropped #598).
• Strong server-side validation: every(id => typeof id === 'string'), dedup via Set, and strict resolution (collections.length !== uniqueCollectionIds.length → 422) that fails loudly instead of partially writing. The unresolved-ids warning log with userId is good observability.
• The onboardingTopics key choice is a deliberate, well-commented fix for the layout/page-data shadowing collision with the home page's own topics key — confirmed real (home +page.server.ts exposes a differently-shaped topics).
• Prisma conventions followed cleanly: select→where clause-key order, satisfies CollectionFindManyArgs, CollectionGetPayload<typeof args> row typing, no as const.
• Thorough new test file covering 401/415/400/422/500 paths, dedup, and the all-resolve happy path.

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🤖 aif-code-review · claude-opus-4-8[1m]

[nicholasjjlim]

LGTM 👍

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🤖 aif-code-review · claude-opus-4-8[1m]