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/resolve-call-id.test.ts

@@ -0,0 +1,40 @@
+import { describe, test, expect } from "bun:test"
+import { resolveCallID } from "./resolve-call-id"
+import type { ToolContextWithMetadata } from "./types"
+
+describe("resolveCallID", () => {
+  function makeCtx(overrides: Partial<ToolContextWithMetadata> = {}): ToolContextWithMetadata {
+    return {
+      sessionID: "ses_test",
+      messageID: "msg_test",
+      agent: "sisyphus",
+      abort: new AbortController().signal,
+      ...overrides,
+    }
+  }
+
+  test("#given callID is set #then returns callID", () => {
+    const ctx = makeCtx({ callID: "call_abc" })
+    expect(resolveCallID(ctx)).toBe("call_abc")
+  })
+
+  test("#given only callId is set #then returns callId", () => {
+    const ctx = makeCtx({ callId: "call_def" })
+    expect(resolveCallID(ctx)).toBe("call_def")
+  })
+
+  test("#given only call_id is set #then returns call_id", () => {
+    const ctx = makeCtx({ call_id: "call_ghi" })
+    expect(resolveCallID(ctx)).toBe("call_ghi")
+  })
+
+  test("#given callID and callId are both set #then prefers callID", () => {
+    const ctx = makeCtx({ callID: "preferred", callId: "fallback" })
+    expect(resolveCallID(ctx)).toBe("preferred")
+  })
+
+  test("#given no call ID variants are set #then returns undefined", () => {
+    const ctx = makeCtx()
+    expect(resolveCallID(ctx)).toBeUndefined()
+  })
+})