Fix CI action pin and Rust Clippy lint

[HiveForensicsAI]

Motivation

• Fix the TypeScript conformance job failing because actions/setup-node could not be resolved at the pinned SHA.
• Address Clippy's question_mark lint in the scheduler loop to remove a warning treated as an error.

Description

• Replace the match self.executor.execute(NodeRequest { ... }) pattern with let execution = self.executor.execute(NodeRequest { ... })?; and rework the retry/fail handling to preserve existing retry semantics in crates/knolo-agent/src/runtime/mod.rs.
• Pin actions/setup-node references in .github/workflows/ci.yml and .github/workflows/release.yml to a resolvable immutable v4 commit (actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020).
• No change to runtime behavior is intended; the Rust change only simplifies error propagation to satisfy Clippy while keeping the same retry and terminal-failure flows.

Testing

• Ran cargo fmt --all --check, which succeeded.
• Ran pnpm --filter @knolo/agents check and pnpm --filter @knolo/agents test, and the TypeScript checks and tests passed (4 tests passed).
• Ran git diff --check, which showed no issues in the working tree.
• cargo clippy --workspace --all-targets -- -D warnings and cargo test --workspace could not complete locally because downloads from crates.io failed due to the environment returning HTTP 403 while fetching dependencies.

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Codex Task