fix(plugin): recreate health context in cleanup for restart support

Recreate healthCtx and healthCancel in cleanup() after cancellation
to support plugin restart. Remove nil assignments for these fields
as they need to persist across restart cycles.

This addresses Elezar's concern NVIDIA#2 about why we nil these fields -
we no longer do. The context is recreated fresh for each restart,
ensuring health checks work correctly when the plugin is restarted.

Fixes plugin restart blocker identified in architecture review.

Refs: NVIDIA#1601
Task: 3/6

Co-authored-by: Evan Lezar <elezar@nvidia.com>
Signed-off-by: Carlos Eduardo Arango Gutierrez <eduardoa@nvidia.com>

Author: ArangoGutierrez

AGENTS.md

@@ -21,15 +21,16 @@
   - Lines: 114-118
   - Changes: Remove `context.WithCancel()` call (already done in constructor)
   - Addresses: Cleanup redundant initialization
-  - Commit: (pending)
+  - Commit: d055f1e0c
 
 ### Phase 2: Restart-Safe Cleanup
 
-- [TODO] **Task 3**: Modify `cleanup()` to recreate context after cancellation
+- [DONE] **Task 3**: Modify `cleanup()` to recreate context after cancellation
   - File: `internal/plugin/server.go`
   - Lines: 120-129
   - Changes: Recreate `healthCtx` and `healthCancel` after cancelling for restart support
   - Addresses: Elezar's concern #2 (line 128 - why nil these fields), fixes plugin restart
+  - Commit: (pending)
 
 ### Phase 3: Health Channel Lifecycle
 

internal/plugin/server.go

@@ -128,12 +128,15 @@ func (plugin *nvidiaDevicePlugin) initialize() {
 func (plugin *nvidiaDevicePlugin) cleanup() {
 	if plugin.healthCancel != nil {
 		plugin.healthCancel()
+		// Recreate context for potential plugin restart. The same plugin instance
+		// may be restarted via Start() after Stop(), so we need a fresh context.
+		plugin.healthCtx, plugin.healthCancel = context.WithCancel(plugin.ctx)
 	}
 	plugin.healthWg.Wait()
 	plugin.server = nil
 	plugin.health = nil
-	plugin.healthCtx = nil
-	plugin.healthCancel = nil
+	// Do not nil healthCtx or healthCancel - they are needed for restart
+	// and are recreated above if they were cancelled
 }
 
 // Devices returns the full set of devices associated with the plugin.