AgentBoot v1.3: Cursor support and verified OpenCode offline

[bit-cook]

Summary

• Adds official Cursor support with pinned Linux AppImage hashes, Windows Authenticode verification, macOS codesign + notarization checks, and an AgentBoot-owned per-user install/uninstall lifecycle.
• Adds verified OpenCode offline support with pinned opencode-ai@1.18.25, platform native binaries (regular + x64 baseline), runtime binary selection, and Node-free OpenCode-only offline packages.
• Updates docs, site, and release workflow so Cursor and OpenCode are first-class across Linux, Windows, Intel macOS, and Apple Silicon lifecycle checks.

Evidence

• 163 Python tests pass.
• Real Linux OpenCode offline build, install, opencode --version, uninstall, and config preservation pass.
• Cursor lifecycle tests cover hash verification, non-official redirect rejection, unmarked directory refusal, and safe uninstall.
• Generated web assets, package hashes, shell/Python/JS/workflow syntax, and diff checks pass.