test: raise coverage for covers, abs, calibre and opds

[vavallee]

Summary

Test only. No production code changes, so no changelog fragment.

Package	Before	After
internal/covers	66.2%	87.3%
internal/abs	71.3%	87.4%
internal/calibre	76.7%	88.9%
internal/opds	78.8%	99.6%

What the new *_coverage_test.go files exercise:

• covers: every image format, the 10 MB cap (and exactly 10 MB accepted), damaged file rewrite, rename failure cleaning up its temp file, unwritable and misconfigured stores.
• abs client: API error decoding variants, malformed JSON, 5xx retry and timeout retry with the backoff cut short by context cancellation (no real waits), SSRF refusal of link-local and metadata base URLs, ScanNotifier reading credentials at call time.
• abs import: rollback restoring rows, upserts, author matcher, enumerator checkpoints, file inspection.
• calibre: pull delivery, plugin client errors, cover materialisation, syncer, rollback.
• opds: per user scoping in every feed (authors, author, series list, series, recent, book) including legacy owner 0 rows and ErrNotFound instead of empty feeds for other users' entities, plus store error propagation.

All remote APIs are httptest servers or scripted transports; files live in temp dirs; DB tests use db.OpenMemory.

Test plan

• gofmt -l clean
• go vet on the four packages
• golangci-lint v2.11.4 on the four packages: 0 issues
• go test -count=1 -cover on the four packages: pass
• go test -race -count=1 on the four packages: pass

No production bugs surfaced.

🤖 Generated with Claude Code

https://claude.ai/code/session_016fJcCVbNnKsmj2MAAMwWj9

[github-actions]

Test-only PR (+5569 / 0). No production code touched, all additions are *_coverage_test.go files. Notes below.

OPDS user scoping (highest-priority area) — the new tests in internal/opds/builder_coverage_test.go cover the properties that matter most:

• Every feed type (authors, author, series list, series, recent, book) is exercised for a scoped user, an admin (user 0), and the legacy owner-0 rows.
• Cross-user entity access correctly returns ErrNotFound rather than an empty feed — this is the right behaviour; an empty feed would leak existence.
• TestBuildSeries_SkipsBooksThatFailToLoad (line 5583): when GetByID returns a store error, the series is surfaced as ErrNotFound for the requesting user. That conflates a real storage failure with "no accessible books", which could silently hide transient DB errors. This is testing existing production behaviour, not new code, so not a blocker — but worth a glance to confirm the BuildSeries implementation intentionally swallows that error.

ABS client / SSRF test (TestValidateBaseURLSecure, line 82): link-local IPv4 (169.254.169.254) and IPv6 (fe80::1) are both refused. Good.

Test infra — db.OpenMemory() throughout, httptest.NewServer for all remote APIs, t.TempDir() for file tests, SQLite trigger injection (covImpEnv.failOn) for narrow write-failure paths. All correct patterns.

ScanNotifier DB-close behaviour (TestScanNotifier_Lifecycle, line 517): a settings read failure after database.Close() is expected to silently act as "unconfigured" rather than return an error. The test is documenting existing behaviour; fine as-is.

No new dependencies, no production code changes.

— 🤖 Bindery triage bot (automated). Reply to correct me; a human will see it.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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