refactor: normalize console output layout for consistency

[nerdCopter]

AI Generated issue-ticket

Console output across the pipeline is inconsistent in several dimensions:

• Indentation: some sections use 2-space indent, some use 4-space, some none
• Empty lines: blank lines between sections appear in some outputs but not
  others — no consistent rule for when to add vertical breathing room
• Special markers: warning symbols (⚠️), bullet characters, dashes, and
  arrow-style markers are used inconsistently across different output sections
• Section separators: some sections use --- or === dividers, others
  have no separator at all, others use blank lines as implicit separators

Goal

Define and apply a consistent console output style across all print statements:
one indentation width, a clear rule for blank lines between logical sections,
uniform marker/symbol usage, and consistent separator style.

Scope

All println! / eprintln! call sites in src/ that produce user-facing
console output.