[codex] speed up interactive startup refresh

[Pimpmuckl]

Summary

• remove the blocking usage refresh from the TUI startup path so the first menu renders from cached account data
• keep usage windows fresh in the background, with auto-start prefiltering accounts that cannot need a ping yet
• serialize repository snapshot writes and make background refresh writes conditional so account switches cannot be overwritten by stale refreshes

Validation

• cargo fmt --check
• cargo test
• cargo clippy --all-targets --all-features -- -D warnings
• cargo build --release --target-dir target\fast-startup-check
• review-suite normal: local signoff clean

[Pimpmuckl]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. What shall we delve into next?

Reviewed commit: 3552e6f93a

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