fix: print program

[deemp]

Closes #108 and fixes printing without a --single flag.

stack run -- --single --rules-yaml ./eo-phi-normalizer/test/eo/phi/rules/yegor.yaml program.phi

before:

⟦ a ↦ ξ.b (c ↦ ⟦ ⟧).d (ρ ↦ ⟦ b ↦ ⟦ c ↦ ∅, d ↦ ⟦ φ ↦ ξ.ρ.c ⟧ ⟧ ⟧) ⟧

after:

{ ⟦ a ↦ ξ.b (c ↦ ⟦ ⟧).d (ρ ↦ ⟦ b ↦ ⟦ d ↦ ⟦ φ ↦ ξ.ρ.c, ν ↦ ⟦ Δ ⤍ 00- ⟧ ⟧, c ↦ ∅, ν ↦ ⟦ Δ ⤍ 00- ⟧ ⟧ ⟧) ⟧ }

---

stack run -- --rules-yaml ./eo-phi-normalizer/test/eo/phi/rules/yegor.yaml program.phi

before:

Rule set based on Yegor's draft
Input:
{ ⟦ a ↦ ⟦ b ↦ ⟦ c ↦ ∅, d ↦ ⟦ φ ↦ ξ.ρ.c ⟧ ⟧, e ↦ ξ.b (c ↦ ⟦ ⟧).d ⟧.e ⟧ }
====================================================
Result 1 out of 1:
⟦ a ↦ ξ.b (c ↦ ⟦ ⟧).d (ρ ↦ ⟦ b ↦ ⟦ d ↦ ⟦ φ ↦ ξ.ρ.c, ν ↦ ⟦ Δ ⤍ 00- ⟧ ⟧, c ↦ ∅, ν ↦ ⟦ Δ ⤍ 00- ⟧ ⟧ ⟧) ⟧
----------------------------------------------------

after:

Rule set based on Yegor's draft
Input:
{ ⟦ a ↦ ⟦ b ↦ ⟦ c ↦ ∅, d ↦ ⟦ φ ↦ ξ.ρ.c ⟧ ⟧, e ↦ ξ.b (c ↦ ⟦ ⟧).d ⟧.e ⟧ }
====================================================
Result 1 out of 1:
{ ⟦ a ↦ ξ.b (c ↦ ⟦ ⟧).d (ρ ↦ ⟦ b ↦ ⟦ d ↦ ⟦ φ ↦ ξ.ρ.c, ν ↦ ⟦ Δ ⤍ 00- ⟧ ⟧, c ↦ ∅, ν ↦ ⟦ Δ ⤍ 00- ⟧ ⟧ ⟧) ⟧ }
----------------------------------------------------

---

PR-Codex overview

This PR updates the CLI help message and refactors the printing logic in Main.hs.

Detailed summary

• Updated CLI help message for a better description
• Refactored printing logic for single normalized expression output
• Improved error handling for empty results
• Refactored printing logic for steps in the main function

✨ Ask PR-Codex anything about this PR by commenting with /codex {your question}