feat(config): configurable auto_approve and claude dir

[krober]

adds two new config options to ~/.config/rtk/config.toml under [hooks]:

• auto_approve (bool, default true) — controls whether the hook bypasses Claude Code's permission prompt
  • false = commands still get rewritten to rtk <cmd> but user is prompted before
    execution
  • env override: RTK_HOOK_AUTO_APPROVE=0
• claude_dir (path, optional) — custom Claude Code data directory for hook installation
  • useful for non-default setups
  • env override: CLAUDE_CONFIG_DIR
  • cli override: rtk init -g --claude-dir /path

supporting changes:

• rtk rewrite --hook-json — moves JSON construction from the shell hook into Rust, so
  permission decisions are config-driven
• hook script simplified to a dumb pipe (version bumped to 3)
• consolidated env var parsing with parse_bool_env() — accepts 1/true/yes, everything
  else is falsy
• resolve_telemetry_enabled() now uses the same cascading pattern (env var → config →
  default)