Enforce Readable Control-Flow Spacing in Agent-Authored Source

## Context Control-flow statements are not consistently separated into visual paragraphs across the source tree, and agent-authored edits can reintroduce the inconsistency. The repository needs deterministic enforcement that improves readability without changing runtime behavior or adding the rule to ordinary contributor lint workflows. ## Acceptance criteria - Conditionals, loops, switches, try blocks, and adjacent statements follow the agreed visual-spacing convention. - Comment placement and same-line statement forms are handled without changing semantics. - Codex and Claude structured-edit and stop hooks apply the same deterministic check and formatting behavior. - Regular lint, lint-staged, and contributor scripts remain independent from the agent-only enforcement. - The repository-wide cleanup is verified as behavior-preserving. ## Implementation Tracked by #2350.