distill --plan silently ignored with text-based config

[noahgift]

Bug

apr distill --config text-distill.yaml --plan silently ignores the --plan flag for text-based distillation configs, erroring with "—stage generate required" instead of showing a plan.

Root Cause

In crates/apr-cli/src/commands/distill.rs, the run_text_config_mode() function (line 585) accepts _plan_only but never uses it (underscore prefix intentionally suppresses warning):

fn run_text_config_mode(
    config: &TextDistillConfig,
    config_path: &Path,
    stage: Option<&str>,
    _plan_only: bool,  // line 589: SILENTLY IGNORED
    json_output: bool,
) -> Result<()> {
    match stage {
        Some("generate") => run_text_generate(config, config_path, json_output),
        // ...
        None => Err(CliError::ValidationFailed(
            "--stage generate required with text-based distillation config.".into()
        )),
    }
}

Compare with the logit KD config path (line 567) which correctly handles plan_only.

Expected Behavior

apr distill --config text-distill.yaml --plan --json should show a plan (config summary, estimated token count, stage descriptions) instead of erroring.

Fix

Add plan_only handling before the stage match, similar to how run_config_mode() handles it for logit KD configs at line 567.