fix(cli): thread --config through kebab eval run/aggregate/compare (facade-rule)

Cmd::Eval now loads Config via cli.config (same pattern as all other
subcommands) before dispatching to the inner match.  Each arm now calls
the *_with_config variant:

  run_eval(&opts)             → run_eval_with_config(&cfg, &opts)
  compute_aggregate(run_id)   → compute_aggregate_with_config(&cfg, run_id)
  store_aggregate(run_id, ..) → store_aggregate_with_config(&cfg, run_id, ..)
  Compare already called compare_runs_with_config but sourced cfg from
  Config::load(None) — that redundant load is removed; cfg comes from
  the shared binding above.

Fixes the same facade-rule regression pattern as P3-5 / P4-3: previously
`kebab --config /build/dogfood/config.toml eval run` silently evaluated
the XDG-default (empty) KB instead of the dogfood KB.

Also fixes runner.rs test that hardcoded rag-v2 after commit 5719969
bumped the default prompt_template_version to rag-v3.

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

crates/kebab-eval/tests/runner.rs

@@ -215,7 +215,7 @@ fn runner_records_config_snapshot_with_versions() {
     assert!(snap.pointer("/llm/model_id").is_some());
     assert_eq!(
         snap.pointer("/prompt_template_version"),
-        Some(&serde_json::Value::String("rag-v2".to_string())),
+        Some(&serde_json::Value::String("rag-v3".to_string())),
     );
     assert!(snap.pointer("/score_gate").is_some());
     assert!(snap.pointer("/rrf_k").is_some());