feat: 配列/Mapリテラル糖衣構文の実装とネームスペース解決の改善計画

- ArrayLiteral/MapLiteralのAST定義追加
- パーサーで[...]と{...}構文をサポート
- MIR Builderでnew Box() + push/setへのdesugaring実装
- テストケースとスモークスクリプト追加
- CURRENT_TASK.mdにネームスペース解決Phase-1計画を追記
- 3段階解決順序（ローカル→エイリアス→プラグイン）の設計合意

docs/reference/language/using.md

@@ -1,4 +1,4 @@
-# using — Imports and Namespaces (Phase 15)
+# using — Imports and Namespaces (Phase 15+)
 
 Status: Accepted (Runner‑side resolution). Selfhost parser accepts using as no‑op and attaches `meta.usings` for future use.
 
@@ -9,6 +9,50 @@ Policy
   - Registers modules into an internal registry for path/namespace hints.
 - Selfhost compiler (Ny→JSON v0) collects using lines and emits `meta.usings` when present. The bridge currently ignores this meta field.
 
+## Namespace Resolution (Runner‑side)
+- Goal: keep IR/VM/JIT untouched. All resolution happens in Runner/Registry.
+- Default search order (3 stages, deterministic):
+  1) Local/Core Boxes (nyrt)
+  2) Aliases (nyash.toml [imports] / `needs … as …`)
+  3) Plugins (short name if unique, otherwise qualified `pluginName.BoxName`)
+- On ambiguity: error with candidates and remediation (qualify or define alias).
+- Modes:
+  - Relaxed (default): short names allowed when unique.
+  - Strict: require plugin prefix (env `NYASH_PLUGIN_REQUIRE_PREFIX=1` or nyash.toml `[plugins] require_prefix=true`).
+- Aliases:
+  - nyash.toml `[imports] HttpClient = "network.HttpClient"`
+  - needs sugar: `needs plugin.network.HttpClient as HttpClient` (file‑scoped alias)
+
+## Plugins
+- Unified namespace with Boxes. Prefer short names when unique.
+- Qualified form: `network.HttpClient`
+- Per‑plugin control (nyash.toml): `prefix`, `require_prefix`, `expose_short_names`
+
+## `needs` sugar (optional)
+- Treated as a synonym to `using` on the Runner side; registers aliases only.
+- Examples: `needs utils.StringHelper`, `needs plugin.network.HttpClient as HttpClient`, `needs plugin.network.*`
+
+## nyash.toml keys (MVP)
+- `[imports]`/`[aliases]`: short name → fully qualified
+- `[plugins.<name>]`: `path`, `prefix`, `require_prefix`, `expose_short_names`
+
+## Index and Cache (Runner)
+- Build a Box index once per run to make resolution fast and predictable:
+```
+struct BoxIndex {
+    local_boxes: HashMap<String, PathBuf>,
+    plugin_boxes: HashMap<String, Vec<PluginBox>>,
+    aliases: HashMap<String, String>,
+}
+```
+- Maintain a small resolve cache per thread:
+```
+thread_local! {
+    static RESOLVE_CACHE: RefCell<HashMap<String, ResolvedBox>> = /* ... */;
+}
+```
+- Trace: `NYASH_RESOLVE_TRACE=1` prints resolution steps (for debugging/CI logs).
+
 Syntax
 - Namespace: `using core.std` or `using core.std as Std`
 - File path: `using "apps/examples/string_p0.nyash" as Strings`
@@ -34,6 +78,28 @@ static box Main {
 }
 ```
 
+Qualified/Plugins/Aliases examples
+```nyash
+# nyash.toml
+[plugins.network]
+path = "plugins/network.so"
+prefix = "network"
+require_prefix = false
+
+[imports]
+HttpClient = "network.HttpClient"
+
+# code
+needs plugin.network.HttpClient as HttpClient
+
+static box Main {
+  main(args) {
+    let a = new HttpClient()         # alias
+    let b = new network.HttpClient() # qualified
+  }
+}
+```
+
 Runner Configuration
 - Enable using pre‑processing: `NYASH_ENABLE_USING=1`
 - Selfhost pipeline keeps child stdout quiet and extracts JSON only: `NYASH_JSON_ONLY=1` (set by Runner automatically for child)
@@ -42,4 +108,3 @@ Runner Configuration
 Notes
 - Phase 15 keeps resolution in the Runner to minimize parser complexity. Future phases may leverage `meta.usings` for compiler decisions.
 - Unknown fields in the top‑level JSON (like `meta`) are ignored by the current bridge.
-