test: unit tests for app/ with regression coverage + PR workflow

[Copilot]

Adds Vitest unit tests for app/, a test script, and a pull-request workflow.

Merged main (branch was 87 commits behind) and resolved both conflicts:

• yarn.lock — both hunks were the tools submodule hash; the submodule itself merged cleanly to main's commit, so main's hashes are the correct side.
• .github/workflows/test.yml — main already has an unrelated test.yml, which this branch had overwritten. Main's file is restored and the unit-test CI now lives in its own unit-tests.yml.

Running the tests

yarn test

yarn test:watch for watch mode, npx vitest run <path> to isolate a file. CI runs yarn test on every pull request via .github/workflows/unit-tests.yml.

Regression detection

The point of the suite is to fail when behaviour changes, so the export-rename path was checked by mutation rather than assumed: removing : from the forbidden-character set in cleanFilename fails 8 tests across 2 files.

To get there, buildExportImageNames() was extracted so the whole chain the export screen actually runs — creation date → user filename format → forbidden-character sanitising → collision suffixes — is covered end to end, instead of only its individual pieces.

The same extract-then-test approach was applied to sync folder filtering: SyncWorker's two private filter methods moved into app/services/sync/folderFilter.ts (the worker delegates to it, behaviour unchanged) so the rules can be pinned — an empty folder list means "no filter", and documents in no folder are excluded once a filter is active.

Fixes to tests already on this branch

• exportUtils.test.ts re-declared the export regex inline and asserted against that copy. It tested a duplicate, so editing the real regex could never fail it. Removed — the real cleanFilename is covered in utils.common.test.ts.
• matrix.test.ts actually tested color_matrix.ts. Renamed to color_matrix.test.ts; a real matrix.test.ts now covers getPageColorMatrix (filter selection, brightness/contrast composition, NaN handling).
• Timezone fragility. A date assertion passed locally and failed under UTC. TZ is now pinned to UTC in the Vitest config — this app formats dates into filenames, so this would have been a recurring CI flake.

New coverage

Area	What is pinned
utils/exportUtils	export filename pipeline, collision suffixes
utils/matrix	page colour matrix selection and composition
utils/pkpass	barcode formats, transit icons, display-name fallbacks, field alignment
services/api	queryString URL building and parameter extraction
services/sync/folderFilter	per-service folder filtering rules
services/sync/types	each sync type owns a unique single bit, in 32-bit range
services/sync/BaseSyncService	stored-settings round-trip, per-service update isolation

Test harness

• ApplicationSettings is now an in-memory store that resets between tests, so settings-dependent behaviour can be exercised instead of only default values.
• Native plugins are mocked and the webpack DefinePlugin globals plus NativeScript's .common.ts platform resolution are mirrored in the Vitest config. This unblocks importing pkpass, api and locale, which previously failed at import time.

251 tests across 14 files. New files typecheck against tsconfig.test.json and pass ESLint.

Not covered, and why

• app/components/** (Svelte) — no component test setup; would need a renderer.
• app/models/OCRDocument.ts — transitively imports the NativeScript UI layer and cannot be imported under Vitest. Documented in .claude/CLAUDE.md along with the extract-the-pure-logic workaround.
• app/services/documents.ts — SQL-backed; needs a database fixture rather than unit tests.

Two things worth a maintainer decision

1. .github/workflows/test.yml on main runs echo "${{ toJSON(secrets) }}", which writes every repository secret into the build log. It is workflow_dispatch-only, so triggering it needs maintainer access, but logs are readable by anyone with read access. Left untouched here as out of scope — worth deleting and rotating those secrets.
2. app/services/trashUtils.ts is unreferenced. The shipping trash logic is SQL-backed in documents.ts, so the existing trash.test.ts guards code the app never runs. Left as-is: either wire the module in or drop it.