Fix Linear team lookup — use teams filter instead of team(key:)

[riddim-developer-bot]

Why

The `resolve_team` query used `team(key: $key)` which Linear's API doesn't support — the `team` root field only accepts `id`. Caused `GRAPHQL_VALIDATION_FAILED` on every handler run after the Bearer and state-filter fixes landed. Discovered and confirmed by running the script locally against the real Linear API before pushing.

What changed

• `resolve_team`: switched from `team(key: $key)` to `teams(filter: { key: { eq: $key } })` and updated parsing to read from `teams.nodes[0]`
• Updated the corresponding test fixture and state-filter query assertion to match

Test plan

22/22 unit tests pass. Script tested locally end-to-end — exits cleanly and creates a Linear issue.