feat: add --store filtering across multi-store commands

[Wangnov]

Summary

• add a global --store cli|app|configured|all selector for status, sync, bucket switch, and watch
• keep rollout-writing backfill guards scoped to all discovered stores while writing only selected stores
• reject --store on commands that do not operate on stores
• isolate multi-store tests from an inherited CODEX_SQLITE_HOME

Tests

• cargo test
• cargo clippy --all-targets -- -D warnings
• cargo run -- --store app print-service-config (expected failure)
• cargo run -- status --store cli

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[Wangnov]

✅ 已随这条 stack 通过快进合并落到 main(本 PR 的提交 ebc2902 已在 main,HEAD=ebc2902)。作为已合并部分关闭。