docs: add Discord community link, drop SECURITY.md

Add a Discord badge to the README badge row and a chat invite in the
Contributing section (both English and Simplified Chinese). Remove
SECURITY.md and its references; private vulnerability reporting stays
available through GitHub's repository setting.

Claude-Session: https://claude.ai/code/session_01ABey161AUxhgmJC3PRoYtF

README.md

@@ -13,6 +13,7 @@
 [![CI](https://github.com/l0ng-ai/tty7/actions/workflows/ci.yml/badge.svg)](https://github.com/l0ng-ai/tty7/actions/workflows/ci.yml)
 [![Version](https://img.shields.io/github/v/tag/l0ng-ai/tty7?label=version&color=ff8a5c)](https://github.com/l0ng-ai/tty7/releases)
 [![License](https://img.shields.io/badge/license-Apache--2.0-blue)](LICENSE)
+[![Discord](https://img.shields.io/badge/Discord-join%20chat-5865F2?logo=discord&logoColor=white)](https://discord.gg/s3dethqz2V)
 
 [**Install**](#-install) · [**Benchmarks**](#-benchmarks) · [**Shortcuts**](#️-shortcuts) · [**Contributing**](#-contributing)
 
@@ -128,8 +129,8 @@ The full list — and any overrides — lives in **Settings → Keybindings**.
 
 ## 🤝 Contributing
 
-Bug reports and PRs are welcome. Security issues go through
-[SECURITY.md](SECURITY.md); notable changes land in the
+Bug reports and PRs are welcome. Questions, ideas, or just want to say hi? Come
+hang out on [Discord](https://discord.gg/s3dethqz2V). Notable changes land in the
 [CHANGELOG](CHANGELOG.md).
 
 ## 📝 License

README.zh-CN.md

@@ -13,6 +13,7 @@
 [![CI](https://github.com/l0ng-ai/tty7/actions/workflows/ci.yml/badge.svg)](https://github.com/l0ng-ai/tty7/actions/workflows/ci.yml)
 [![Version](https://img.shields.io/github/v/tag/l0ng-ai/tty7?label=version&color=ff8a5c)](https://github.com/l0ng-ai/tty7/releases)
 [![License](https://img.shields.io/badge/license-Apache--2.0-blue)](LICENSE)
+[![Discord](https://img.shields.io/badge/Discord-%E5%8A%A0%E5%85%A5%E7%BE%A4%E7%BB%84-5865F2?logo=discord&logoColor=white)](https://discord.gg/s3dethqz2V)
 
 [**安装**](#-安装) · [**基准测试**](#-基准测试) · [**快捷键**](#️-快捷键) · [**参与贡献**](#-参与贡献)
 
@@ -117,7 +118,8 @@ tty7 以设备速度读取 PTY，并在渲染路径之外成批解析输出，
 
 ## 🤝 参与贡献
 
-欢迎提 bug 和 PR。安全问题请走 [SECURITY.md](SECURITY.md)；重要改动都记在
+欢迎提 bug 和 PR。有问题、有想法，或者只是想唠两句，欢迎来
+[Discord](https://discord.gg/s3dethqz2V) 一起玩。重要改动都记在
 [CHANGELOG](CHANGELOG.md)。
 
 ## 📝 许可证

SECURITY.md

@@ -1,28 +0,0 @@
-# Security Policy
-
-## Supported versions
-
-Only the latest release receives security fixes.
-
-## Reporting a vulnerability
-
-Please report vulnerabilities **privately** — do not open a public issue.
-
-Use [GitHub private vulnerability reporting](https://github.com/l0ng-ai/tty7/security/advisories/new)
-— "Report a vulnerability" under the repository's **Security** tab.
-
-You should get an initial response within a few days. Please include a
-reproduction if you can — a byte sequence, a clipboard payload, or a shell
-snippet is ideal.
-
-## Scope notes
-
-A terminal emulator's attack surface is unusual: untrusted input arrives as
-escape sequences from anything you `cat`, `ssh`, or paste. Reports in these
-areas are especially valuable:
-
-- Escape-sequence parsing (VT/OSC/CSI handling, including the daemon-side
-  scanners).
-- Clipboard and paste handling (e.g. bracketed-paste escapes).
-- Shell-integration scripts and the `ZDOTDIR` bootstrap.
-- The daemon's Unix socket / named pipe protocol and its process lifecycle.

openwiki/operations/development-testing-release.md

@@ -77,7 +77,7 @@ Windows icon embedding is handled separately by `build.rs` via `winresource` whe
 
 ## Security-sensitive areas
 
-`SECURITY.md` highlights a terminal emulator's unusual input surface: untrusted escape sequences can come from `cat`, `ssh`, remote programs, and paste. Be extra careful with:
+A terminal emulator has an unusual input surface: untrusted escape sequences can come from `cat`, `ssh`, remote programs, and paste. Be extra careful with:
 
 - VT/CSI/OSC parsing and scanner recovery,
 - clipboard store/load and paste handling,