I think the conditions are sufficiently self-descriptive.

This fixes the incorrect comment and uses $HOME (rather than ~) to be a
little bit more explicit.

Also, our script is named ghostty-integration, not ghostty.zsh, so
update that part of the comment, too.

If we're running a too-old version of zsh, we exit early. This skipped
the _ghostty_file cleanup path below.

Locate our ghostty binary using $GHOSTTY_BIN_DIR rather than searching
the PATH.

This value is always set to a non-empty string, and we only need this
value after we've determined that 'ssh_hostname' is non-empty.

In bash and zsh, we also don't need to check for the 'ghostty' command
before we attempt to add the target to the cache. That command will
safely fail silently if it's not available.

- Update Bash script (baseline): Simplify cache checking logic, clarify
"xterm-ghostty terminfo" message, remove unnecessary ssh_opts from
terminfo installation, remove extra success message
- Align ZSH/Fish/Elvish with updated Bash: Remove extra success
messages, adopt simplified cache checking, standardize setup messages
- Apply Elvish improvements: Remove unnecessary try/catch blocks, use
idiomatic error handling patterns
- Apply Fish improvements: Replace string pattern matching with
efficient `contains` checks on split features list

- Default ssh_term to xterm-256color to eliminate fallback assignments
- Remove base64 and replace infocmp -Q2 with standard -0 -x options for
compatibility
- Use process substitution instead of intermediate ssh_config variable
- Always set TERM explicitly since ssh_term is always defined

- Simplify feature detection to use single wildcard check
- Replace ssh_env array with simple ssh_term string variable
- Use TERM environment prefix instead of save/restore pattern
- Remove unnecessary backgrounded subshell for cache operations

- Remove complex ssh_exported_vars tracking and local environment
modification in favor of trusting Ghostty's local environment
- Replace regex patterns with glob-based feature detection for better
performance
- Fix local variable declaration consistency throughout
- Streamline logic while maintaining all functionality