refactor: drop internal bridge/ffi layers; exporter family lands

Single-lib cleanup: the per-crate src/bridge/ and src/ffi.rs layers are
gone (oakundo/oakcommon/oaknode/oaktimeline/oakcodec/oakaudio/
oakrender/oaktask/oakplugin/oakstorage); cross-crate calls are plain
Rust, CHandle marshalling shrinks to the oakengine boundary, and tests
call the Rust APIs directly (pure C-ABI wrapper tests removed where
the domain layer already covers the behavior).

exporter.h family implemented: oakengine_export_render (CLI contract),
oakengine_export_render_with_params (was a stub), last_error and
progress callback; synchronous path reuses task_create_export +
start_sync. Fixes on the way: oaktask video ticket self-deadlock,
audio params dropped on the export path, codec encoder AAC slicing and
H.264 time base. Real-mp4 tests cover both entry points, progress and
the illegal-argument matrix.

Also: oakstorage session maps null project handles to None (version-
info path), configstore test double literal 3.14 -> 3.15 (clippy PI
lint), oakaudio output callback scratch buffer + env-aware P1 test,
cli media round-trip test uses a generated 16-frame clip (no more
minute-long debug runs).

crates/oakplugin/tests/common/mod.rs

@@ -20,9 +20,8 @@
 //! 运行时装配成 oak-test-plugin.ofx.bundle）：filter 上下文、
 //! Double 参数 gain、双 clip（Source/Output）。插件未构建时相关
 //! 用例经 [`skip`] 提前返回。
-//! 测试桩在库内（bridge::render::stub，`--features test-stubs`）：
-//! 全链路像素路径可在 cargo test 跑通；真实链路在 standalone
-//! ctest。本文档的 run 命令见 crate README。
+//! 单库化后像素路径经 oakrender 值模型（`oakrender::texture::Texture`）
+//! 驱动；渲染 goldens 待该迁移落地。
 
 use std::path::PathBuf;