test(core): add unit tests for least-covered core modules

[devin-ai-integration]

Summary

packages/core (the headless business-logic package) was the least-covered TypeScript package — only the 3 platform-storage files had tests (~1% statement coverage), while ~87 other source files had none. This PR adds unit tests for its pure-logic modules, taking coverage of the tested files to ~89% statements / ~92% lines. No source code was changed — tests only.

How coverage was assessed

Ran vitest --coverage per package. packages/core stood out: 90 source files, 3 tested. packages/views had 7 test files, apps/web had 1. The Go backend (server/) is already broadly tested (30+ _test.go files). So the largest, most testable coverage gap was packages/core, and within it the pure functions / zustand stores that need no DOM or network mocking.

Modules covered (all previously 0%)

• utils.ts — timeAgo boundary behavior (just now / m / h / d) and shortID.
• issues/config/status.ts & priority.ts — ordering, board-column exclusion of cancelled, config completeness for every enum value.
• projects/config.ts — project status/priority ordering + config completeness.
• issues/stores/view-store.ts — the richest target: filter toggles, the non-obvious hideStatus/showStatus branches (e.g. hideStatus with no active filter selects ALL_STATUSES minus one), clearFilters preserving view mode/sort, card-property and collapsed-column toggles. Tested via the createIssueViewStore factory for isolation.
• issues/stores/{selection,draft,recent-issues,issues-scope}-store.ts — set/dedup logic, draft merge/clear/hasDraft, recent-visit dedup + 20-item cap, scope switching.
• navigation/store.ts — onPathChange excludes /login and /pair/ prefixes but records paths that merely contain them.
• modals/store.ts — open/close and data handling.
• i18n/store.ts — setLanguage/initializeFromCookie using minimal document/window global stubs (core runs in a Node, non-DOM test env).

Notes

• No production code touched; pnpm --filter @multica/core test goes from 8 → 74 passing tests. tsc --noEmit passes; eslint reports no issues on the new files.
• Environment note: the repo's vitest/rolldown toolchain requires Node ≥20.19; use Node 22 (matches CI) to run the suite locally.

Link to Devin session: https://app.devin.ai/sessions/c4819c9679c64321bf2f6e5268263691
Requested by: @killerleon94

[devin-ai-integration]

🤖 Devin AI Engineer

I'll be helping with this pull request! Here's what you should know:

✅ I will automatically:

• Address comments on this PR. Add '(aside)' to your comment to have me ignore it.
• Look at CI failures and help fix them

Note: I can only respond to comments from users who have write access to this repository.

⚙️ Control Options:

• Disable automatic comment, CI, and merge conflict monitoring