fix: workflow inference chain — surface llama-server errors, user-turn-last, bundle-relative prompts

- LlamaCppInferenceProvider: check HTTP status and surface the real error body instead of masking it as a ChatCompletionResponse deserialization failure
- PromptRenderer: render the live conversation layer (L1) last so the user turn is the final message (fixes Qwen 'No user query found' 500 when L3 recall is present)
- TomlWorkflowLoader: resolve stage prompts relative to the workflow file's own dir (bundle), CWD-independent; config-dir fallback for globals
- SessionOrchestrator: hard-fail a stage whose declared prompt can't resolve (was a silent user-less request)
- move healthcheck prompts next to the example workflow (examples/workflows/prompts/)

infrastructure/workflow/src/main/kotlin/com/correx/infrastructure/workflow/TomlWorkflowLoader.kt

@@ -15,6 +15,7 @@ import com.fasterxml.jackson.dataformat.toml.TomlMapper
 import com.fasterxml.jackson.module.kotlin.kotlinModule
 import com.fasterxml.jackson.module.kotlin.readValue
 import java.nio.file.Path
+import kotlin.io.path.exists
 import kotlin.io.path.readText
 
 private data class WorkflowFile(
@@ -67,10 +68,17 @@ class TomlWorkflowLoader(
         val raw = path.readText()
         val file = runCatching { mapper.readValue<WorkflowFile>(raw) }
             .getOrElse { throw WorkflowValidationException("Failed to parse workflow TOML: ${it.message}") }
-        return file.toWorkflowGraph()
+        return file.toWorkflowGraph(path.parent)
     }
 
-    private fun WorkflowFile.toWorkflowGraph(): WorkflowGraph {
+    private fun resolvePromptPath(raw: String, workflowDir: Path?): String {
+        val p = Path.of(raw)
+        if (p.isAbsolute) return raw
+        val candidate = workflowDir?.resolve(raw)
+        return if (candidate != null && candidate.exists()) candidate.toString() else raw
+    }
+
+    private fun WorkflowFile.toWorkflowGraph(workflowDir: Path?): WorkflowGraph {
         val startId = StageId(start)
         val stageMap = stages.associate { s ->
             StageId(s.id) to StageConfig(
@@ -84,8 +92,8 @@ class TomlWorkflowLoader(
                 tokenBudget = s.tokenBudget,
                 maxRetries = s.maxRetries,
                 metadata = buildMap {
-                    s.prompt?.let { put("prompt", it) }
-                    s.systemPrompt?.let { put("systemPrompt", it) }
+                    s.prompt?.let { put("prompt", resolvePromptPath(it, workflowDir)) }
+                    s.systemPrompt?.let { put("systemPrompt", resolvePromptPath(it, workflowDir)) }
                 },
             )
         }