fix(opencode): introduce `childrenIDs` session field to allow for fast children lookup

[goniz]

Fixes #8437 #3526

[github-actions[bot]]

Hey! Your PR title session: introduce childrenIDs field to allow for fast children lookup doesn't follow conventional commit format.

Please update it to start with one of:

• feat: or feat(scope): new feature
• fix: or fix(scope): bug fix
• docs: or docs(scope): documentation changes
• chore: or chore(scope): maintenance tasks
• refactor: or refactor(scope): code refactoring
• test: or test(scope): adding or updating tests

Where scope is the package name (e.g., app, desktop, opencode).

See CONTRIBUTING.md for details.

[github-actions[bot]]

The following comment was made by an LLM, it may be inaccurate:

No duplicate PRs found