Prepare Stack CLI 0.5.4 with clear arrow terminals

[konojunya]

Background

Stack Engine 0.9.1 corrects arrow-marked route terminals so the marker keeps a readable final orthogonal approach when the adjacent section can move safely. The native CLI needs the same released rendering behavior.

Implementation Approach

• Bump the CLI source version to 0.5.4 while preserving 0.5.3 as the currently activated distribution version until release verification completes.
• Pin the registry-only stack-engine =0.9.1 crate and its verified checksum.
• Refresh the license audit, generated manual, release-contract fixtures, and release notes.

Testing Approach

• Rust 1.85 and stable test/clippy/doc gates.
• Formatter and template conformance against the pinned specification.
• All release, distribution, schema, Aqua-registry, and archive contract tests.
• Exact coverage gates: 92.01% lines, 96.58% functions, and 92.12% regions.
• Registry-only Cargo publish dry run, generated CLI asset verification, standalone SVG validation, and release binary/doctor smoke checks.

Review Perspectives / Points of Concern

• Commands, configuration, JSON contracts, theme behavior, and Rust 1.85 remain unchanged.
• Exact SVG bytes intentionally change for affected routes.
• Public channels remain on 0.5.3 until the immutable 0.5.4 release and clean-install checks succeed.