feat: clearer open-error for a valid-but-unsupported SQLite database

[ivmakk]

Description

.db is not unique to Thumbs.db. When a user opens a valid SQLite database that isn't a supported thumbnail cache (e.g. a media-library index with no image BLOBs), Thumbscope now shows a clear "SQLite database, not a thumbnail cache" headline instead of the generic "Unsupported file" one. Detection was already correct - the file is header-matched as SQLite and never sent to the OLE2 parser; only the user-facing raw message and the renderer's friendlyError headline needed to say so plainly. Adds a SFW synthetic sample and end-to-end coverage of the rejection.

Related issue

[Feature] Clearer open-error for a valid-but-unsupported SQLite .db (+ synthetic sample) (#53)

Type of change

Feature

How has this been tested?

• npm test (233 pass, 0 fail) - includes a new node --test contract in photothumb.test.ts that runs the real thrown UNSUPPORTED_SQLITE_MESSAGE through friendlyError and asserts it maps to the SQLite headline (drift caught at the fast tier, not only e2e), plus the existing friendlyError and photothumb reject cases.
• npm run typecheck clean across the node, web, and e2e projects.
• npm run test:e2e -- formats.spec.ts -g media-index - launches the real Electron app against the committed sample/media-index.db, asserts the error banner is visible, contains "SQLite database", is not the generic "Unsupported file" fallback, and renders no grid.
• CLI cross-check: npm run cli -- list sample/media-index.db prints the new raw message.

Checklist

• Self-reviewed the diff
• npm test and npm run typecheck pass
• Docs updated (README / CLAUDE.md / DESIGN.md) where relevant
• Added a CHANGELOG.md ## [Unreleased] entry (user-facing change) or n/a (internal-only)
• No real local paths or PII in tracked files (public repo)

[Copilot]

Pull request overview

This PR improves the user-facing error experience when opening a valid SQLite .db that is not a supported thumbnail cache, so users see an explicit “SQLite database” headline instead of the generic unsupported-file fallback. It updates the core error string thrown for unsupported SQLite schemas and adds both fast-tier and e2e coverage to prevent message-to-headline drift.

Changes:

• Introduces a dedicated “SQLite database – not a thumbnail cache…” headline in friendlyError() and aligns the core thrown message to include the “SQLite database” signal.
• Adds a node-tier contract test to ensure the real thrown SQLite rejection message continues to map to the SQLite-specific headline.
• Adds an e2e assertion for the error banner via a new data-testid, verifying the SQLite-specific headline and an empty grid.

Reviewed changes

Copilot reviewed 7 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/renderer/src/lib/errors.ts	Adds SQLite-specific mapping in friendlyError() to avoid the generic unsupported fallback.
src/renderer/src/lib/errors.test.ts	Adds unit coverage ensuring SQLite-mentioning raw text maps to the SQLite headline.
src/renderer/src/App.tsx	Adds data-testid="open-error" to make the open-error banner reliably selectable in e2e tests.
src/core/photothumb.ts	Defines and uses UNSUPPORTED_SQLITE_MESSAGE for unsupported SQLite schema cases.
src/core/photothumb.test.ts	Adds a contract test asserting the real unsupported-SQLite message maps to the SQLite headline.
e2e/specs/formats.spec.ts	Adds an e2e scenario asserting SQLite DB rejection uses the SQLite headline and renders no grid.
CHANGELOG.md	Documents the improved messaging for unsupported SQLite .db opens.