[changelog] Add changelog for v1.0.11

> [!CAUTION]
> Protected files were modified in this change.
> This pull request is in `request_review` mode and requires explicit human scrutiny before merge.
>
> Protected files: `CHANGELOG.md`

Adds the `v1.0.11` changelog entry to `CHANGELOG.md`.

Covers 6 highlighted features and 4 other changes across all SDKs, plus 3 new contributors.

> Generated by [Release Changelog Generator](https://github.com/github/copilot-sdk/actions/runs/31818422729) · sonnet46 39.5 AIC · ⌖ 9.24 AIC · ⊞ 8.1K · [◷](https://github.com/search?q=repo%3Agithub%2Fcopilot-sdk+%22gh-aw-workflow-id%3A+release-changelog%22&type=pullrequests)

---

> [!NOTE]
> This was originally intended as a pull request, but the git push operation failed.
>
> **Original error:** pushSignedCommits: refusing unsigned push for branch 'changelog/v1.0.11-47e41bc8a651a7bc': Signed-commit payload violates file-protection policy (request_review): CHANGELOG.md
>
> **Workflow Run:** [View run details and download bundle artifact](https://github.com/github/copilot-sdk/actions/runs/31818422729)
>
> The bundle file is available in the `agent` artifact in the workflow run linked above.

To create a pull request with the changes:

```sh
# Download the artifact from the workflow run
gh run download 31818422729 -n agent -D /tmp/agent-31818422729

# Fetch the bundle into a temporary ref, then update the local branch
git fetch /tmp/agent-31818422729/aw-changelog-v1.0.11.bundle refs/heads/changelog/v1.0.11:refs/bundles/create-pr-changelog-v1-0-11-47e41bc8a651a7bc-d2cf7a75
git update-ref refs/heads/changelog/v1.0.11-47e41bc8a651a7bc refs/bundles/create-pr-changelog-v1-0-11-47e41bc8a651a7bc-d2cf7a75
git checkout changelog/v1.0.11-47e41bc8a651a7bc
# Ensure the working tree matches the updated branch
git reset --hard
# Remove the temporary bundle ref
git update-ref -d refs/bundles/create-pr-changelog-v1-0-11-47e41bc8a651a7bc-d2cf7a75

# Push the branch to origin
git push origin changelog/v1.0.11-47e41bc8a651a7bc

# Create the pull request
gh pr create --title '[changelog] Add changelog for v1.0.11' --base main --head changelog/v1.0.11-47e41bc8a651a7bc --repo github/copilot-sdk
```

从 CHANGELOG.md 和链接的 Release Changelog Generator 工作流运行记录开始。下载 agent artifact，使用文档中记录的 git 命令获取并 checkout 生成的 changelog 分支，然后在推送该分支并打开 issue 中描述的 pull request 之前，验证 changelog 条目。

由索引模型根据 Issue 内容生成。