[MugdhoAI]

Summary

• Restore the document collection sidebar expanded by default, with upload, session privacy, accurate upload limits, indexed document count, clear action, and collapsed query syntax help.
• Keep a compact, centered purple hero and wide native search form; the supporting line is centered and uses no dash or hyphen.
• Keep result limits, optional Gemini rewriting, readable results, and a quiet empty state. Gemini only rewrites plain text queries and does not search documents or generate answers.
• Style uploader and secondary controls to match the dark purple workspace.
• Add UI smoke coverage for the sidebar, hero copy, successful search, and no results.

Validation

• python -m pytest -q: 87 passed
• python -m ruff check src tests: passed
• git diff --check: passed
• Search evaluation: MRR 1.0, NDCG@5 0.9516, Recall@5 0.9375
• Local desktop browser preview verified the expanded sidebar, centered copy, upload controls, and aligned search controls. A narrow viewport screenshot was not available in this environment.
• GitHub checks for the latest commit are running.

Deployment

This pull request is not merged. The deployed Streamlit app will use the update after the PR is approved and merged.