fix: guard zsh compdef call to prevent error before compinit (nearai#422)

* fix: guard zsh compdef call to prevent error before compinit

The generated ironclaw.zsh completions file calls compdef without
checking if it exists. Users who source this file before compinit
runs in their .zshrc get "compdef: command not found" on every
terminal open.

Wrap the call with the standard (( $+functions[compdef] )) guard.

Closes nearai#420

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix(completions): apply compdef guard during zsh generation

Instead of hand-patching the generated ironclaw.zsh file (which is
fragile and lost on regeneration), patch the compdef call in the
generation code itself. The Zsh output is post-processed to wrap
`compdef _ironclaw ironclaw` with a `$+functions[compdef]` guard.

Regenerated ironclaw.zsh from the patched code to stay in sync.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

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Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: zmanian