docs: synchronize "What's New" section between README and docs

- Add Version 1.35.0 batch/album normalization feature to docs/index.md
- Add "Album Batch normalization" to Features list in docs/index.md
- Update CLAUDE.md with Documentation Synchronization section
- Fix markdown linting issues in CLAUDE.md (blank lines around lists/headings)
- Ensure both README.md and docs/index.md stay in sync for future updates

This ensures users see consistent information whether they're viewing
the GitHub README or the hosted documentation site.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: slhck

CLAUDE.md

@@ -69,6 +69,19 @@ The tool supports three normalization types defined in `NORMALIZATION_TYPES`:
 
 When committing, YOU MUST use conventional commits.
 
+### Documentation Synchronization
+
+When updating the "What's New" section or the "Features" list, YOU MUST keep **both** files in sync:
+
+1. **README.md** (root of repository) - The "🆕 What's New" and "✨ Features" sections
+2. **docs/index.md** (documentation homepage) - The "🆕 What's New" and "✨ Features" sections
+
+These sections should always contain identical content. When adding a new feature or version announcement:
+
+- Update both files simultaneously
+- Ensure formatting and wording are consistent
+- Verify links work in both contexts (GitHub links in README, relative links in docs)
+
 ### CLI Changes Checklist
 
 When adding, removing, or modifying CLI options, YOU MUST:
@@ -81,23 +94,28 @@ When adding, removing, or modifying CLI options, YOU MUST:
 This ensures users have accurate documentation and working shell completions for all CLI flags.
 
 ### Dependencies
+
 The project uses:
+
 - `tqdm` for progress bars
 - `ffmpeg-progress-yield` for FFmpeg progress monitoring
 - `colorlog` for colored logging
 - `mutagen` for metadata handling
 - `colorama` (Windows only) for colored terminal output
 
 ### File Structure
+
 - `src/ffmpeg_normalize/` - Main package directory
 - `tests/` - Test files and test media samples
 - `docs/` - MKdocs documentation source
 - `completions/` - Shell completion scripts
 
 ### Testing
+
 Tests use pytest and include actual media files in the `tests/` directory. The test suite calls the CLI directly using `python -m ffmpeg_normalize` to test the full pipeline.
 
 ### Requirements
+
 - Python 3.9+
 - FFmpeg binary must be available in PATH
 - The tool checks for FFmpeg loudnorm filter availability at runtime

docs/index.md

@@ -27,20 +27,37 @@ Batch processing of several input files is possible, including video files.
 - **Docker support** — Run via Docker container
 - **Python API** — Use programmatically in your Python projects
 - **Shell completions** — Available for bash, zsh, and fish
+- **Album Batch normalization** – Process files jointy, preserving relative loudness
 
 ## 🆕 What's New
 
-**Version 1.34.0** brings selective audio stream normalization! You can now:
+- Version 1.35.0 has **batch/album normalization** with `--batch`. It preserves relative loudness between files! Perfect for music albums where you want to shift all tracks by the same amount.
 
-- **Normalize specific audio streams** with `-as/--audio-streams` (e.g., `-as 1,2` to normalize only streams 1 and 2)
-- **Normalize only default audio streams** with `--audio-default-only` (useful for files with multiple language tracks)
-- **Keep other streams unchanged** with `--keep-other-audio` (copy non-selected streams without normalization)
+    Example:
 
-Example: `ffmpeg-normalize input.mkv -as 1 --keep-other-audio` normalizes stream 1 and copies all other audio streams unchanged.
+    ```bash
+    ffmpeg-normalize album/*.flac --batch -nt rms -t -20
+    ```
 
-**Recent additions:**
+    shifts the entire album so the average RMS is -20 dB, preserving the original relative loudness as mastered.
 
-- **Shell completions** (v1.31.0) — Tab completion for bash, zsh, and fish shells. See the [completions directory](https://github.com/slhck/ffmpeg-normalize/tree/master/completions) for installation instructions.
+- Version 1.34.0 brings **selective audio stream normalization**! You can now:
+
+  - Normalize specific audio streams with `-as/--audio-streams` (e.g., `-as 1,2` to normalize only streams 1 and 2)
+  - Normalize only default audio streams with `--audio-default-only` (useful for files with multiple language tracks)
+  - Keep other streams unchanged with `--keep-other-audio` (copy non-selected streams without normalization)
+
+    Example:
+
+    ```bash
+    ffmpeg-normalize input.mkv -as 1 --keep-other-audio
+    ```
+
+    normalizes stream 1 and copies all other audio streams unchanged.
+
+Other recent additions:
+
+- **Shell completions** (v1.31.0) — Tab completion for bash, zsh, and fish shells. See the [installation guide](../getting-started/installation/#shell-completions) for setup instructions.
 - **`--lower-only` option** — Prevent audio from increasing in loudness, only lower it if needed (works with all normalization types).
 
 See the [full changelog](about/changelog.md) for all updates.