json: add v2 JsonDoc/JsonNode plugin with runtime provider switch; vendored yyjson + FFI; loader resolve(name)->method_id; PyVM JSON shims; smokes + CI gate; disable MiniVmPrints fallbacks by default

- plugin_loader_v2: store per-Box resolve() from TypeBox FFI; add resolve_method_id() and use in invoke_instance_method
- plugin_loader_unified: resolve_method() falls back to loader’s resolve when TOML lacks method entries
- nyash.toml: register JsonDocBox/JsonNodeBox methods (birth/parse/root/error; kind/get/size/at/str/int/bool)
- plugins/nyash-json-plugin:
  * serde/yyjson provider switch via env NYASH_JSON_PROVIDER (default serde)
  * vendored yyjson (c/yyjson) + shim; parse/root/get/size/at/str/int/bool implemented for yyjson
  * TLV void returns aligned to tag=9
- PyVM: add minimal JsonDocBox/JsonNodeBox shims in ops_box.py (for dev path)
- tests/smokes: add jsonbox_{parse_ok,parse_err,nested,collect_prints}; wire two into min-gate CI
- tools: collect_prints_mixed now uses JSON-based app
- MiniVmPrints: move BinaryOp and fallback heuristics behind a dev toggle (default OFF)
- CURRENT_TASK.md: updated with provider policy and fallback stance

plugins/nyash-json-plugin/c/yyjson/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2020 YaoYuan <ibireme@gmail.com>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.