feat: add rich ui for converting

docs/cli.md

@@ -157,26 +157,46 @@ Convert papers from PDF to Markdown using MinerU.
 **Options:**
 - `--library PATH`: Specify library directory
 - `--paper-id ID`: Convert specific paper only
+- `--retry-failed`: Retry papers with failed conversion status
+- `--force`: Force reconvert all papers (including successful ones)
+- `--no-ui`: Disable rich UI display (useful for scripting)
 
 **Examples:**
 ```bash
-# Convert all pending papers
+# Convert all pending papers (with rich UI)
 paperlib convert
 
+# Retry failed conversions
+paperlib convert --retry-failed
+
+# Force reconvert all papers
+paperlib convert --force
+
 # Convert specific paper
 paperlib convert --paper-id arxiv-2212_06340
 
+# Convert without UI (for scripts)
+paperlib convert --no-ui
+
 # Convert in specific library
 paperlib convert --library ~/research
 ```
 
 **Behavior:**
-- Processes papers with `conversion_status: pending`
-- Uses MinerU for PDF to Markdown conversion
+- Processes papers with `conversion_status: pending` (or failed with `--retry-failed`)
+- Uses MinerU for PDF to Markdown conversion with CPU pipeline backend
+- Shows rich UI with progress bar and live MinerU output (unless `--no-ui`)
 - Updates metadata with conversion status
 - Creates conversion logs in `logs/` directory
+- Post-processes markdown to fix image references (`images/` → `assets/`)
 - Handles conversion failures gracefully
 
+**Rich UI Features:**
+- Progress bar showing papers converted
+- Live streaming of MinerU output
+- Current paper being processed
+- Color-coded output (errors in red, progress in blue, etc.)
+
 ---
 
 ### `paperlib reindex`