feat(yahweh-meta-runtime): promover short_hash y preview_value desde nakui-explorer

Continúa la integración de apps nakui al stack yahweh. Los
helpers visuales que nakui-explorer tenía locales y son reusables
suben a yahweh-meta-runtime/format.

yahweh-meta-runtime:
- short_hash(h: &[u8; 32]) -> String: hex de los primeros 4 bytes.
- preview_value(v: &Value, max: usize) -> String: JSON one-liner
  truncado con "..." (edge case max < 3 sin panic).
- 5 tests nuevos.

nakui-explorer:
- Nueva dep yahweh-meta-runtime.
- Borrado helpers locales (short_uuid + short_hash + preview_value)
  + 4 tests duplicados.
- Imports desde yahweh-meta-runtime.

Tests: 42→47 yahweh-meta-runtime, 7→3 nakui-explorer (los 3 que
quedan son específicos del explorer: load_log, breakdown,
missing_file). Resto intacto.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/apps/nakui-explorer/Cargo.toml

@@ -7,6 +7,7 @@ description = "Explorador GPUI del event log de Nakui: timeline de seeds + morph
 
 [dependencies]
 nakui-core = { path = "../../modules/nakui/core" }
+yahweh-meta-runtime = { path = "../../modules/ui_engine/libs/meta-runtime" }
 gpui = { workspace = true }
 serde_json = { workspace = true }
 uuid = { workspace = true, features = ["serde"] }