Add Zed editor config and fix Kiro CLI completion in IDE terminals

[Okabe-Junya]

What

• Track ~/.config/zed/settings.json under dotfiles via file-level symlink.
• Add cask "zed" to the Brewfile and allowlist .config/zed/ in .gitignore.
• Declare extensions (html, material-icon-theme) with auto_install_extensions.
• Set Zed terminal font_family to Hack Nerd Font Mono to match Terminal.app.
• Pass Q_NEW_SESSION=1 through terminal.env so the existing kiro-cli shell init (added in feat(zsh): integrate kiro cli shell completion #130) resets state for shells spawned by Zed.

Why

• Zed config was previously unmanaged, so settings did not reproduce across machines.
• Terminal.app's default profile (Clear Dark) uses HackNFM-Regular (Hack Nerd Font Mono); aligning Zed's integrated terminal keeps glyph rendering consistent.
• Zed launches the shell directly (no figterm PTY wrapper), so Q_TERM / QTERM_SESSION_ID inherited from the parent are stale. Q_NEW_SESSION=1 tells the kiro-cli pre-init to clear them and re-attach.