refactor(plugin): share timeout helpers between process and process::v4

Delete the 5 copy-pasted timeout helpers in process/v4.rs (CALL_TIMEOUT_DEFAULT, call_timeout, request_timeout, execute_code_timeout, base_max_floor, request_kind) and reuse the canonical process.rs versions, now pub(crate). Prevents floor drift between v1 and v4 paths. Net: +3 / -59, no behavior change. Verified: cargo check -p ocs_plugin_api clean, cargo test -p ocs_plugin_api --lib --features host (92 passed).

crates/ocs_plugin_api/src/process.rs

@@ -193,7 +193,7 @@ fn call_timeout() -> Duration {
 
 /// Per-request-kind timeout floors. The user-configured default is raised to
 /// these minima so that no request kind can be configured into an unsafe value.
-fn request_timeout(kind: &'static str) -> Duration {
+pub(crate) fn request_timeout(kind: &'static str) -> Duration {
     base_max_floor(call_timeout(), kind)
 }
 
@@ -228,7 +228,7 @@ fn base_max_floor(base: Duration, kind: &'static str) -> Duration {
     base.max(floor)
 }
 
-fn request_kind(req: &HostRequest) -> &'static str {
+pub(crate) fn request_kind(req: &HostRequest) -> &'static str {
     match req {
         HostRequest::GetManifest => "GetManifest",
         HostRequest::GetRibbon => "GetRibbon",