Move releases, self-update and links to ELY-Open-Source on GitHub

- kigi-env: update_base_url defaults to
  api.github.com/repos/ELY-Open-Source/Kigi-CLI/releases.
- install.sh / install.ps1: resolve releases from the same API.
- /feedback and the no-session feedback fallback open GitHub issues/new;
  /docs opens the README on GitHub.
- SECURITY, NOTICE, AGENTS, CONTRIBUTING: GitHub repo, issues and fork-based
  pull requests replace git.zacharyzhang.com and AGit.

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

crates/codegen/kigi-tui/src/slash/commands/docs.rs

@@ -10,7 +10,7 @@ use crate::slash::command::{AppCtx, ArgItem, CommandExecCtx, CommandResult, Slas
 
 /// Online docs landing page (hardcoded like other TUI deep-links; the
 /// project README is the docs entry point for the repo-hosted docs).
-pub const BUILD_DOCS_URL: &str = "https://git.zacharyzhang.com/ZacharyZhang-NY/Kigi-CLI/src/branch/main/README.md";
+pub const BUILD_DOCS_URL: &str = "https://github.com/ELY-Open-Source/Kigi-CLI/blob/main/README.md";
 
 /// Open How-to Guides or online Build docs.
 pub struct DocsCommand;