feat(whaleflow): replay recorded workflow outputs

[Hmbown]

Summary

• Adds a crate-only WhaleFlow replay executor over recorded leaf/control records.
• Computes stable SHA-256 leaf input hashes from workflow/leaf metadata and resolved dependency outputs.
• Marks missing records as replay_diverged by default instead of synthesizing output or calling a model.
• Adds focused replay tests for recorded leaf output, whole-workflow replay, divergence, live-replay opt-in, stable hashing, and recorded Cond/Expand/LoopUntil control decisions.

Stewardship Notes

• Advances WhaleFlow: deterministic replay from recorded leaf outputs #2673 as a narrow maintainer slice.
• Preserves the broader WhaleFlow direction from @AdityaVG13's feat: add WhaleFlow — declarative multi-agent workflow orchestration #2482/Feat/whaleflow cost tracking #2486 without merging the draft runtime/worktree/provider scope.
• Does not add a runtime replay command, worktree replay, provider calls, or live replay fallback. allow_live_replay currently errors unless a live provider is explicitly implemented later.

Verification

• cargo test -p codewhale-whaleflow --offline (initial lock refresh)
• cargo test -p codewhale-whaleflow --locked
• cargo clippy -p codewhale-whaleflow --all-targets --locked -- -D warnings
• cargo fmt --all -- --check
• ./scripts/release/check-versions.sh
• ./scripts/release/check-ohos-deps.sh
• git diff --check

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