feat(pdf-reader): add PDF fallback skill for when agents lack PDF capability

Submitted by: https://github.com/divitkashyap

## What
Added  — a skill that provides automatic fallback when an agent states it cannot read PDFs. Intercepts the limitation and extracts PDF text using command-line tools with user confirmation for installation.

## Why
When AI agents lack native PDF reading capability, they either fail or give generic responses. This skill provides a complete fallback workflow:
1. Detect when agent says 'I cannot read PDFs' (or similar phrases)
2. Check for available tools (pdftotext → pdfplumber → pymupdf)
3. If no tool found, ask user permission to install
4. Extract PDF text to temp file
5. Continue with original user task

## Complementary to minimax-pdf-read
This skill differs from  (PR #51):
- minimax-pdf-read: User explicitly asks to extract text from a PDF (active)
- pdf-reader: Agent says it can't read PDFs → fallback workflow (passive)

Both can coexist — they serve different trigger conditions.

## Tool Priority
1. pdftotext (poppler-utils) — Preferred, fastest, system-level
2. pdfplumber (Python) — Fallback if poppler not available
3. pymupdf (Python) — Alternative Python fallback

## Platform Support
- macOS: Homebrew (brew install poppler) or pip
- Linux: apt-get/dnf install poppler-utils or pip
- Windows: winget/chocolatey or pip

## Key Features
- Automatic detection of agent PDF limitation
- Multi-tool fallback strategy
- User confirmation before installation
- Platform-specific installation commands
- Layout preservation (-layout flag)
- Page range extraction (-f, -l flags)
- Error handling for encrypted/protected PDFs

## Example Triggers
- 'I cannot read PDFs'
- 'I don't have the ability to read PDFs'
- 'I can't access PDF content'

## Files
- skills/pdf-reader/SKILL.md — Complete skill with workflow
- README.md, README_zh.md — Updated with new entry

## Validation
All 15 skills pass: python .claude/skills/pr-review/scripts/validate_skills.py ✅

Author: divitkashyap

README_zh.md

@@ -23,6 +23,7 @@
 | `minimax-xlsx` | 打开、创建、读取、分析、编辑或验证 Excel/电子表格文件（.xlsx、.xlsm、.csv、.tsv）。支持通过 XML 模板从零创建 xlsx、使用 pandas 读取分析、零格式损失编辑现有文件、公式重算与验证、专业财务格式化。 | Official |
 | `minimax-docx` | 基于 OpenXML SDK（.NET）的专业 DOCX 文档创建、编辑与排版。三条流水线：从零创建新文档、填写/编辑现有文档内容、应用模板格式并通过 XSD 验证门控检查。 | Official |
 | `vision-analysis` | 使用视觉 AI 模型分析、描述和提取图像信息。支持描述、OCR 文字识别、UI 界面审查、图表数据提取和物体检测。基于 MiniMax VL API，OpenAI GPT-4V 作为备选。 | Community |
+| `pdf-reader` | 自动检测 Agent 无法读取 PDF 的情况，并使用命令行工具（pdftotext/poppler-utils）提供文本提取后备方案。支持自动检测、用户确认后安装、多平台支持（macOS、Linux、Windows）。 | Community |
 | `minimax-multimodal-toolkit` | 通过 MiniMax API 生成语音、音乐、视频和图片内容 — MiniMax 多模态使用场景的统一入口。涵盖 TTS（文字转语音、声音克隆、声音设计、多段合成）、音乐（带词歌曲、纯音乐）、视频（文生视频、图生视频、首尾帧、主体参考、模板、长视频多场景）、图片（文生图、图生图含角色参考），以及基于 FFmpeg 的媒体处理（格式转换、拼接、裁剪、提取）。 | Official |
 
 ## 安装