Epic: Redesign authentication and multi-file conversion workflow

[DenWin]

Goal

Track the redesign of authentication and the multi-file conversion workflow.

The original proposal was split because it combines independent visual, security, upload, capability-model, settings, filename-parser, and validation-framework work. Each child issue can now be designed, implemented, tested, and reviewed separately.

Child issues

• Modernize the login screen #10
• Support explicit local, OIDC, and built-in authentication modes #11
• Redesign the multi-file upload queue and file actions #12
• Add capability-aware target and converter selection #13
• Add shared batch defaults and per-file conversion settings #14
• Add safe output filename templates with live preview #15
• Establish TDD, retrospective characterization, and real-world assessment #16

Required engineering workflow

All new implementation follows the red-green-refactor workflow in #16. Existing test-worthy behavior receives retrospective characterization coverage with demonstrated test sensitivity. Feature completion requires behavior-level automated tests plus applicable real-world evidence; implementation alone is not sufficient.

Recommended sequence

1. Establish TDD, retrospective characterization, and real-world assessment #16 Establish the tracer test, fixture manifest, assessment schema, and fast CI foundation.
2. Support explicit local, OIDC, and built-in authentication modes #11 Persist authenticated sessions across restarts.
3. Redesign the multi-file upload queue and file actions #12 Establish the upload queue and accessible file actions.
4. Add capability-aware target and converter selection #13 Introduce capability-aware target/converter selection.
5. Add shared batch defaults and per-file conversion settings #14 Add typed shared defaults and per-file overrides.
6. Add safe output filename templates with live preview #15 Add safe filename templates and previews.
7. Modernize the login screen #10 Apply the final login visual refresh alongside the shared responsive/accessibility language.

The test framework begins first and grows incrementally with each vertical feature slice. Some visual work from #10 and #12 may proceed in parallel, but settings and filename templates should build on the typed capability model rather than adding unstructured form fields.

Overall completion criteria

• Returning users can remain authenticated across container restarts for a bounded session lifetime.
• Login and conversion screens are compact, responsive, and accessible.
• Users can upload and manage up to 20 files.
• Reasonable targets and converter implementations are capability-filtered.
• Batch defaults and per-file overrides are typed and server-validated.
• Output filename templates are previewed, sanitized, and collision-safe.
• New behavior was developed through an observable red-green-refactor cycle, and existing behavior has retrospective characterization coverage.
• Fast tests gate pull requests and the full real-world corpus assesses release candidates.
• Assessment reports contain reproducible environment data, format-appropriate quality results, and explicit regression decisions.