fix(kernel,server,tui,inference): generic resource gauge + F-002/F-003/F-004

- generic SystemResourceProbe: owner-agnostic /proc/meminfo system RAM
  overlaid on the vendor GPU probe, wired on both managed and static paths
  so the VRAM/GPU/RAM gauge renders with an external llama-server (was dormant)
- F-002: classify provider 4xx (e.g. llama.cpp 400) as terminal, not retryable
  (except 408/429); stops retrying deterministic request failures to exhaustion
- F-003: FileSystemPromptLoader expands leading ~ / ~/ to user home
- F-004: map InferenceFailedEvent + RetryAttemptedEvent to new
  ServerMessage.InferenceFailed / RetryAttempted, decoded+rendered in tui-go;
  ArtifactContentStoredEvent explicitly mapped to null (internal, no warn)
- tests: tilde expansion, SystemResourceProbe (static/managed/fail-soft)

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

@@ -8,12 +8,21 @@ class FileSystemPromptLoader(
     private val configDir: Path = Path.of(System.getProperty("user.home"), ".config", "correx", "prompts"),
 ) : PromptLoader {
     override fun load(path: String): String {
-        val local = Path.of(path)
+        val expanded = expandTilde(path)
+        val local = Path.of(expanded)
         if (local.exists()) return local.readText()
 
-        val fromConfig = configDir.resolve(path)
+        val fromConfig = configDir.resolve(expanded)
         if (fromConfig.exists()) return fromConfig.readText()
 
         throw PromptNotFoundException("Prompt not found: $path (searched: $local, $fromConfig)")
     }
+
+    // Expand a leading `~` / `~/...` to the user home so a config-supplied home path resolves
+    // instead of being concatenated literally onto [configDir] (F-003).
+    private fun expandTilde(path: String): String = when {
+        path == "~" -> System.getProperty("user.home")
+        path.startsWith("~/") -> System.getProperty("user.home") + path.substring(1)
+        else -> path
+    }
 }

infrastructure/workflow/src/test/kotlin/com/correx/infrastructure/workflow/FileSystemPromptLoaderTest.kt

@@ -33,6 +33,19 @@ class FileSystemPromptLoaderTest {
         assertContains(ex.message!!, configDir.toString())
     }
 
+    @Test
+    fun `expands leading tilde to user home (F-003)`() {
+        val home = System.getProperty("user.home")
+        val rel = "correx-tilde-${System.nanoTime()}.md"
+        val file = java.nio.file.Path.of(home, rel).also { it.writeText("home prompt") }
+        try {
+            val loader = FileSystemPromptLoader(configDir = Files.createTempDirectory("unused"))
+            assertEquals("home prompt", loader.load("~/$rel"))
+        } finally {
+            Files.deleteIfExists(file)
+        }
+    }
+
     @Test
     fun `local path takes precedence over configDir`() {
         val localFile = Files.createTempFile("prompt", ".md").also { it.writeText("local") }