feat(axbuild): improve incremental clippy coverage

[YanLien]

Problem

The previous clippy flow was too time-consuming for regular CI usage. Running broad clippy checks too often made feedback slower, while the incremental path still needed enough coverage to catch issues in crates affected by a change.

Changes

• Update incremental cargo xtask clippy --since <base> selection:
  • Run directly changed crates with cargo clippy --no-deps.
  • Run affected top-level crates with deps enabled to cover the affected subtree.
  • Recompute runnable affected roots when unsupported top-level crates are skipped.
• Use three-dot git diff for --since so PR checks only consider changes from the current branch.
• Print clippy start time, finish time, and elapsed time.
• Add a scheduled cargo xtask clippy --all job to .github/workflows/starry-apps.yml.
• Update CLAUDE.md to remove stale clippy_crates.csv whitelist references and document the current clippy flow.

Rationale

The new flow keeps PR clippy cheaper by avoiding full-workspace checks on every run. Directly changed crates are checked with --no-deps, while selected top-level affected crates run with deps to preserve coverage of the impacted dependency tree.

The scheduled clippy --all job moves the expensive full-workspace check to a periodic workflow, so CI still gets full coverage without making every PR pay that cost.

Three-dot diff avoids over-selecting crates when the base branch has moved, which prevents unnecessary extra clippy work and accidental full-workspace fallbacks.

Validation

• cargo fmt
• cargo test -p axbuild --lib -- --nocapture
• cargo xtask clippy --package axbuild

[ZR233]

审查通过。

重点检查了增量 clippy 选择逻辑、三点 diff base 处理、直接 changed crate 的 --no-deps 检查、受影响顶层 crate 的 with-deps frontier 选择，以及 sync-lint/clippy 在 workflow 里直接传 --since 后的 fallback 行为。没有发现会漏检或破坏 CI 的阻塞问题。

本地验证：

• cargo fmt --all -- --check
• cargo test -p axbuild --lib -- --nocapture（477 passed）
• cargo xtask clippy --package axbuild
• cargo xtask sync-lint --since origin/dev
• cargo xtask clippy --since origin/dev（选择 1 个 changed package 和 2 个 dependent top-level package，共 12 个 check，全部通过）
• 额外探测：cargo xtask sync-lint --since 0000000000000000000000000000000000000000 会 fallback 到 full scan 并通过；cargo xtask clippy --since 0000000000000000000000000000000000000000 已确认会 fallback 到 full workspace 后中断，避免跑完整 714 个 check。

远端 CI 当前通过。重复/重叠方面，base 里没有等价的三点 diff/frontier/timing 实现；open PR 中 #1031/#1024 只是在 ci.yml 不同区块有普通合并冲突风险，不是同一功能重复实现。