refactor(node): switch oaknode to refcounted value handles, migrate consumers

- all 15 OakNode* handle types become neutral by-value structs
  {ctx, addref, release, abi_version}; shared box in
  src/node/c_api/nodehandle.h with owns flag (borrowed accessors
  return non-owning boxes; graph insertion flips owns off)
- oaktimeline/oaktask/oakrender call sites and their own public
  headers migrated to value handles; identity comparisons in
  timeline/task now compare native pointers
- regressions green: oaknode 96, oaktimeline 117, oaktask 106,
  oakrender 44, oakcommon 193, oakcodec 18, oakaudio 36

include/render/copier.h

@@ -45,17 +45,19 @@ OakRenderProjectCopier *oakrender_project_copier_create(void);
 /** @brief Free the copier AND its copied project. NULL-safe. */
 void oakrender_project_copier_free(OakRenderProjectCopier *copier);
 
-/** @brief (Re)build the copy from `project`. */
+/** @brief (Re)build the copy from `project` (borrowed handle). */
 int oakrender_project_copier_set_project(OakRenderProjectCopier *copier,
-										 OakNodeProject *project);
+										 OakNodeProject project);
 
-/** @brief The copied counterpart of an original node (borrowed), NULL
- *        when the node is not in the copied project. */
-OakNodeNode *oakrender_project_copier_get_copy(
-	OakRenderProjectCopier *copier, OakNodeNode *original);
+/** @brief The copied counterpart of an original node (borrowed handle;
+ *        freeing it only releases the handle box), empty handle when the
+ *        node is not in the copied project. */
+OakNodeNode oakrender_project_copier_get_copy(
+	OakRenderProjectCopier *copier, OakNodeNode original);
 
-/** @brief The copied project (borrowed). */
-OakNodeProject *oakrender_project_copier_get_copied_project(
+/** @brief The copied project (borrowed handle; freeing it only releases
+ *        the handle box). */
+OakNodeProject oakrender_project_copier_get_copied_project(
 	OakRenderProjectCopier *copier);
 
 #ifdef __cplusplus

include/render/manager.h

@@ -24,6 +24,7 @@
 #include <stdint.h>
 
 // See cache.h for why these are same-dir relative includes.
+#include "node/node.h" /* OakNodeNode (by-value handle) */
 #include "cache.h" /* OakCodecFrame */
 #include "color.h" /* OakColorProcessor */
 #include "error.h"
@@ -50,12 +51,6 @@ extern "C" {
  * are no event subscription interfaces.
  */
 
-/**
- * @brief Borrowed node handle (olive::Node) from the oaknode ABI,
- * re-declared here so this header is self-contained.
- */
-typedef struct OakNodeNode OakNodeNode;
-
 /**
  * @brief Create the RenderManager singleton (spawns render/audio
  * threads, loads the configured backend).
@@ -91,11 +86,12 @@ typedef void (*oakrender_frame_ready_fn)(OakCodecFrame *frame, int64_t ts,
  * cancelled with oakrender_cancel_request().
  *
  * @return A positive request id, or a negative OAKRENDER_E_* code
- *         (OAKRENDER_E_INVALID for NULL viewer/callback,
- *         OAKRENDER_E_STATE when the manager is not initialized,
- *         OAKRENDER_E_FAILED when no ticket could be created).
+ *         (OAKRENDER_E_INVALID for an empty viewer handle or NULL
+ *         callback, OAKRENDER_E_STATE when the manager is not
+ *         initialized, OAKRENDER_E_FAILED when no ticket could be
+ *         created).
  */
-int64_t oakrender_request_frame(OakNodeNode *viewer, int64_t ts,
+int64_t oakrender_request_frame(OakNodeNode viewer, int64_t ts,
 								oakrender_frame_ready_fn cb, void *userdata);
 
 /**
@@ -109,11 +105,11 @@ int oakrender_cancel_request(int64_t request_id);
 /**
  * @brief Set the multicam node on the manager's auto-cacher
  * (PreviewAutoCacher::set_multicam_node()). `multicam_or_NULL` is a
- * borrowed oaknode handle to a MultiCamNode (NULL to clear).
+ * borrowed oaknode handle to a MultiCamNode (empty handle to clear).
  *
  * @return OAKRENDER_OK or OAKRENDER_E_STATE.
  */
-int oakrender_set_cacher_multicam(OakNodeNode *multicam_or_NULL);
+int oakrender_set_cacher_multicam(OakNodeNode multicam_or_NULL);
 
 /**
  * @brief Set the display color processor on the manager's auto-cacher

include/render/ticket.h

@@ -64,12 +64,12 @@ enum OakRenderTicketType {
  *        (RenderManager::RenderVideoParams).
  */
 typedef struct oakrender_video_ticket_params {
-	OakNodeNode *output_node; /**< Connected texture output node. */
+	OakNodeNode output_node; /**< Connected texture output node (borrowed). */
 	OakVideoParams video_params; /**< By value (oakcommon handle). */
 	OakAudioParams *audio_params; /**< Borrowed oakcore handle, may be NULL. */
 	int64_t time_num; /**< Frame timestamp as rational. */
 	int64_t time_den;
-	OakNodeColorManager *color_manager; /**< Borrowed, may be NULL. */
+	OakNodeColorManager color_manager; /**< Borrowed, empty ctx = NULL. */
 	int mode; /**< olive::RenderMode::Mode as int. */
 	int force_width; /**< 0/0 = off. */
 	int force_height;
@@ -100,7 +100,7 @@ OakRenderTicket *oakrender_ticket_render_frame(
  * @param params Audio params (borrowed oakcore handle).
  */
 OakRenderTicket *oakrender_ticket_render_audio(
-	OakNodeNode *output_node, int64_t in_num, int64_t in_den,
+	OakNodeNode output_node, int64_t in_num, int64_t in_den,
 	int64_t out_num, int64_t out_den, const OakAudioParams *params,
 	int mode, oakrender_ticket_finished_fn cb, void *userdata);