Fix-GUI-startup-and-refactor-regressions

[Cat-blizzard]

What changed

• Restore the Streamlit script entry point so SlideNote Studio renders instead of showing a blank page.
• Keep resolved provider, model, base URL, and cache directory consistent across note generation, repair calls, cache keys, and usage reports.
• Serialize PDF table extraction around process-global stdout/stderr redirection to avoid races during parallel page extraction.
• Fix the redundancy audit's package naming, relative-import resolution, and known false positives.
• Consolidate duplicated normalized-bbox helpers and remove stale study-pack imports.
• Restore defensive secret redaction in displayed commands.
• Add regression coverage for GUI startup, runtime option resolution, PDF stream restoration, command redaction, and the audit script.

Why

The GUI defined main() but no longer invoked it when Streamlit executed the script, leaving the application body empty. Recent refactors also introduced split runtime configuration between normal note generation and repair/reporting paths, while PDF parallelization made a previously safe process-global stream redirection racy.

Impact

SlideNote Studio now renders normally. LLM cache metadata and usage reports use the same canonical runtime values as actual calls, parallel PDF extraction no longer risks corrupting process output streams, and the redundancy audit produces actionable results.

Validation

• 193 passed
• python -m compileall -q slidenote gui scripts
• Redundancy audit reports no unused imports, unreachable modules, or duplicate function bodies.
• Streamlit was launched locally and verified in a browser: the full first-run UI rendered and the console had no errors.