Auto mode now uses 3.5 Flash; backend definitions respected

What's Changed

• chore(ci): add optimized PR size labeler and batch workflows by @sripasg in https://github.com/google-gemini/gemini-cli/pull/27616
• fix(ci): use pull_request_target trigger to grant write access on fork PRs by @sripasg in https://github.com/google-gemini/gemini-cli/pull/27637
• chore(release): bump version to 0.47.0-nightly.20260602.gcfcecebe8 by @gemini-cli-robot in https://github.com/google-gemini/gemini-cli/pull/27644
• Changelog for v0.46.0-preview.0 by @gemini-cli-robot in https://github.com/google-gemini/gemini-cli/pull/27641
• Respect backend definitions for 3.5 flash and Update auto mode to use 3.5 flash when the flag is enabled. by @DavidAPierce in https://github.com/google-gemini/gemini-cli/pull/27645
• fix(policy): add EBUSY fallback and TOML parse recovery (#19919) by @krishdef7 in https://github.com/google-gemini/gemini-cli/pull/21541
• Changelog for v0.45.0 by @gemini-cli-robot in https://github.com/google-gemini/gemini-cli/pull/27642

Full Changelog: https://github.com/google-gemini/gemini-cli/compare/v0.45.0-nightly.20260602.g665228e98...v0.47.0-nightly.20260604.g4196596f7