feat(pdf-tools): add pdf-tools extension

extensions/pdf-tools/.gitignore

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+node_modules
+vicinae-env.d.ts
+dist
+.DS_Store
+*.log

extensions/pdf-tools/README.md

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+# PDF Tools for Vicinae
+
+An all-in-one PDF toolkit extension for **Vicinae**, ported and expanded from Raycast's PDF Tools. Works seamlessly across **Linux**, **macOS**, and **Windows**.
+
+---
+
+## Features & Commands
+
+### `images-to-pdf` - Convert Images to PDF
+Merge and convert multiple images of any format (`.png`, `.jpg`, `.jpeg`, `.tiff`, `.webp`, `.bmp`, `.gif`, `.avif`, etc.) into a single PDF document.
+- Preserves original image quality and handles EXIF rotation.
+- Blends transparent images cleanly over a solid white background.
+- Sorts pages naturally according to image file names (e.g. `img1`, `img2`, `img10`).
+- Saves the generated PDF directly in the source directory.
+
+### `merge` - Merge PDF Files
+Combines two or more PDF files into a single unified document.
+- Retains source page order and saves the merged file in the same directory.
+
+### `protect` - Protect PDF
+Encrypts a PDF document with military-grade AES-256 password protection in place.
+
+### `unlock` - Unlock PDF
+Removes password encryption and decrypts the document in place.
+
+### `split-by-file-size` - Split PDF by File Size
+Intelligently splits a large PDF into multiple parts based on a maximum file size threshold (in MB) using an optimized binary search algorithm.
+
+### `split-by-page-count` - Split PDF by Page Count
+Divides a PDF document into smaller parts containing a specified number of pages each.
+
+### `watermark` - Add Watermark
+Applies a crisp vector text watermark across all pages of a PDF document with custom text, rotation angle (0° or 45°), and opacity.
+
+---
+
+## Universal File Selection
+
+PDF Tools provides a frictionless file selection experience across all operating systems:
+1. **Active Finder / Explorer Selection**: Directly picks files currently selected in macOS Finder.
+2. **Clipboard Detection**: Automatically detects files copied to the clipboard (GNOME/Wayland clipboard, Windows Explorer clipboard, or copied file paths).
+3. **Native File Picker Fallback**: If no files were previously selected or copied, an interactive native file dialog opens automatically (`zenity` / `kdialog` on Linux, AppleScript dialog on macOS, `OpenFileDialog` on Windows).
+
+---
+
+## Prerequisites & Installation
+
+PDF Tools relies on lightweight system tools for cryptographic operations and image processing.
+
+### 1. `qpdf` (Required for merge, protect, unlock, split)
+- **Linux (Ubuntu/Debian)**: `sudo apt install qpdf`
+- **Linux (Arch/Manjaro)**: `sudo pacman -S qpdf`
+- **Linux (Fedora)**: `sudo dnf install qpdf`
+- **macOS**: `brew install qpdf`
+- **Windows**: `winget install qpdf` (or `choco install qpdf`)
+
+### 2. Python & Pillow (Required for `images-to-pdf`)
+- Ensure Python is installed on your system.
+- Install Pillow:
+  ```bash
+  pip install Pillow
+  ```
+
+---
+
+## Credits
+
+- Ported, enhanced, and maintained for Vicinae by [manuelcontrera](https://github.com/manuelcontrera).
+- Original Raycast extension created by [xilopaint](https://github.com/xilopaint).