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/src/handle.rs

@@ -56,8 +56,8 @@ pub struct RefBox<T: ?Sized> {
 /// The shared ABI value-handle type (single-lib unification, see
 /// `docs/zh/plans/riir/single-lib.md`): one canonical
 /// `{ctx, addref, release, abi_version}` type in `oakcore-rs`, re-exported
-/// here so the crate's `ffi.rs` signatures and handle scaffolding stay
-/// source-compatible. `Send + Sync` come from the shared type.
+/// here so the crate's handle scaffolding stays source-compatible.
+/// `Send + Sync` come from the shared type.
 pub use oakcore_rs::handle::CHandle;
 
 /// addref 的实现：原子 +1。拥有型与借用型共用——借用型只延长盒子
@@ -177,7 +177,7 @@ where
 	}
 }
 
-/// 无返回值版本：panic 被吞并记录日志（经 bridge 的日志回调）。
+/// 无返回值版本：panic 被吞（日志回调待 message 出口接入后补）。
 pub fn guard_void<F>(f: F)
 where
 	F: FnOnce(),