feat: Add enhanced debug logging for plugin VM communication

- Add VM→Plugin and Plugin→VM boundary logging for method calls
- Enhanced debug output for tracking plugin invocation flow
- Added return value type/instance logging for better debugging
- Improved plugin communication traceability

This helps debug issues like the recent 45-day HTTP response debugging saga.
All logging is controlled by NYASH_DEBUG_PLUGIN=1 environment variable.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

docs/development/roadmap/idea/README.md

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+Nyash Dev Ideas / Roadmap Scratchpad
+
+Purpose
+- Quick scratchpad to capture ideas before they get shaped into tasks/PRs.
+- Keep entries short and action-oriented; promote to RFC/docs when stable.
+
+Near-Term (High Impact)
+- Strengthen plugin ABI tester:
+  - Parse `nyash.toml` and verify method_id wiring with minimal invokes (birth + no-arg methods).
+  - Add contract tests for net plugin boxes (HttpRequest/Response/Client/Server).
+  - Fail fast with clear diffs when IDs drift.
+- Make debug logs opt-in (done):
+  - `NYASH_DEBUG_PLUGIN=1` gates VM→Plugin bridge logs.
+  - `NYASH_NET_LOG=1` gates net plugin logs.
+- Regression tests:
+  - Minimal end-to-end for HTTP: get→accept→respond→readBody (body non-empty).
+  - ABI sanity tests per box type (already added for HttpRequestBox).
+
+Identity & Copy Semantics
+- Enforce `is_identity()` and `clone_or_share()` usage across interpreter paths.
+- Audit remaining `clone_box()` callsites; switch to `clone_or_share()` where identity is required.
+- Optional: add dev assertions when PluginBoxV2 instance_id changes unexpectedly in a single flow.
+
+Single Source of Truth for Method IDs
+- Avoid hand-edit drift between plugin code and `nyash.toml`:
+  - Option A: Generate `nyash.toml` from Rust consts (build.rs or small generator).
+  - Option B: Generate Rust method_id consts from `nyash.toml`.
+  - Start with a checker that diffs the two (cheap safety net).
+
+CI / Tooling
+- Add `plugin_contract_*` tests to default CI.
+- Add a `--ci-quiet` profile to suppress debug logs; emit logs only on failure.
+- Introduce a small utility to reserve/randomize test ports to avoid collisions.
+
+Net Plugin Polishing
+- Keep TCP-only path; prefer accepted TCP requests in server.accept (done).
+- Mirror response body into client handle using X-Nyash-Resp-Id (done); document behavior.
+- Add timeouts and clearer error messages for readBody stalls.
+
+Docs
+- Expand `docs/development/box_identity_and_copy_semantics.md` with examples and anti-patterns.
+- Add a quickstart: “How to debug the net plugin” (env flags, key logs, typical pitfalls).
+
+Future Ideas
+- Lightweight codegen for plugin schemas (IDs, arg signatures, returns_result) → toml + Rust.
+- Lint/pass that forbids `clone_box()` on identity boxes in critical paths.
+- Structured logging with categories and levels (trace/info/warn) pluggable to CI.
+
+Notes
+- Keep this file as a living list; prune as items graduate to tracked issues/PRs.
+