fix(inference): tolerate a briefly-absent provider instead of killing the session (#299)

A transient provider connection drop (e.g. OOM-killed llama.cpp mid-request)
collapsed into a hard NoEligibleProviderException that escaped runInference's
try/catch (the route() call sat outside it), propagated past the stage retry
loop, and landed in ServerModule's session-level catch — failing the WHOLE
session even though the failure was retryable and the provider recovered
seconds later.

- SessionOrchestrator.runInference: wrap router.route() in try/catch so
  routing failures become InferenceResult.Failed and flow through the normal
  retryable/backoff/exhaustion machinery instead of escaping.
- DefaultInferenceRouter.route: distinguish "capability never configured on
  any provider" (fail fast, waiting can't help) from "configured but
  currently unhealthy" (bounded wait/backoff — default 3 attempts x 2s —
  re-checking health before declaring NoEligibleProvider terminal).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GeyGFXczJb8RUWGBKmkm6G

testing/contracts/src/test/kotlin/com/correx/testing/contracts/model/inference/DefaultInferenceRouterTest.kt

@@ -13,8 +13,10 @@ import com.correx.core.inference.RoutingStrategy
 import com.correx.testing.fixtures.inference.MockInferenceProvider
 import kotlinx.coroutines.runBlocking
 import org.junit.jupiter.api.Assertions.assertSame
+import org.junit.jupiter.api.Assertions.assertTrue
 import org.junit.jupiter.api.Test
 import org.junit.jupiter.api.assertThrows
+import kotlin.time.Duration.Companion.milliseconds
 
 class DefaultInferenceRouterTest {
 
@@ -157,4 +159,58 @@ class DefaultInferenceRouterTest {
         val result = router.route(stage, setOf(ModelCapability.General), "llama-cpp:sick")
         assertSame(healthy, result)
     }
+
+    // ── bounded wait for a briefly-absent provider (#299) ─────────────────────
+
+    @Test
+    fun `waits for the sole capable provider to recover instead of failing immediately`(): Unit = runBlocking {
+        var healthChecks = 0
+        val recovering = object : InferenceProvider by provider("a", ModelCapability.ToolCalling) {
+            override suspend fun healthCheck(): ProviderHealth {
+                healthChecks++
+                return if (healthChecks < 3) ProviderHealth.Unavailable("connection dropped") else ProviderHealth.Healthy
+            }
+        }
+        val router = DefaultInferenceRouter(
+            registryOf(recovering),
+            firstStrategy(),
+            unavailableRetryAttempts = 5,
+            unavailableRetryDelay = 5.milliseconds,
+        )
+        val result = router.route(stage, setOf(ModelCapability.ToolCalling))
+        assertSame(recovering, result)
+        assertTrue(healthChecks >= 3) { "expected at least 3 health checks, got $healthChecks" }
+    }
+
+    @Test
+    fun `still throws NoEligibleProviderException if the sole provider never recovers within the bound`() {
+        val neverRecovers = MockInferenceProvider(
+            id = ProviderId("a"),
+            declaredCapabilities = setOf(CapabilityScore(ModelCapability.ToolCalling, 1.0)),
+            health = ProviderHealth.Unavailable("still down"),
+        )
+        val router = DefaultInferenceRouter(
+            registryOf(neverRecovers),
+            throwingStrategy(),
+            unavailableRetryAttempts = 2,
+            unavailableRetryDelay = 5.milliseconds,
+        )
+        assertThrows<NoEligibleProviderException> {
+            runBlocking { router.route(stage, setOf(ModelCapability.ToolCalling)) }
+        }
+    }
+
+    @Test
+    fun `fails fast without waiting when the capability was never configured on any provider`(): Unit = runBlocking {
+        val p = provider("a", ModelCapability.General) // does not declare ToolCalling
+        val router = DefaultInferenceRouter(
+            registryOf(p),
+            throwingStrategy(),
+            unavailableRetryAttempts = 5,
+            unavailableRetryDelay = 10_000.milliseconds, // would time the test out if the wait loop ran
+        )
+        assertThrows<NoEligibleProviderException> {
+            router.route(stage, setOf(ModelCapability.ToolCalling))
+        }
+    }
 }