fix(delegate-task): remove kimi from unstable agent detection, harden callID resolution for metadata store

- Remove kimi from auto-detected unstable agents in category-resolver (only gemini/minimax remain)
- Add resolveCallID() to safely resolve callID/callId/call_id variants from tool context
- Use resolveCallID across all 5 delegate task execution paths (sync, background, unstable, continuations)
- Update writing category test to verify kimi runs sync when kimi provider is available
- Add atlas metadata preservation tests confirming tool-execute-after does not clobber metadata

Co-authored-by: factory-droid[bot] <138933559+factory-droid[bot]@users.noreply.github.com>

src/tools/delegate-task/background-task.ts

@@ -4,6 +4,7 @@ import type { FallbackEntry } from "../../shared/model-requirements"
 import { getTimingConfig } from "./timing"
 import { buildTaskPrompt } from "./prompt-builder"
 import { storeToolMetadata } from "../../features/tool-metadata-store"
+import { resolveCallID } from "./resolve-call-id"
 import { formatDetailedError } from "./error-formatting"
 import { getSessionTools } from "../../shared/session-tools-store"
 import { SessionCategoryRegistry } from "../../shared/session-category-registry"
@@ -132,8 +133,9 @@ export async function executeBackgroundTask(
       metadata,
     }
     await ctx.metadata?.(unstableMeta)
-    if (ctx.callID) {
-      storeToolMetadata(ctx.sessionID, ctx.callID, unstableMeta)
+    const callID = resolveCallID(ctx)
+    if (callID) {
+      storeToolMetadata(ctx.sessionID, callID, unstableMeta)
     }
 
     const taskMetadataBlock = sessionId