refactor: rename render_error_sanitized to clarify it is the sanitization boundary

[dean0x]

Location: crates/mds-cli/src/output.rs:495

What: render_error_sanitized describes the transformation (render + sanitize) but not that it is the boundary — the sanitization enforcement point for CWE-150 hardening.

Why deferred: Naming refinement, no behavior change. Better addressed as a dedicated refactor.

Source review: .devflow/docs/reviews/fix-esc-injection-176/2026-07-25_1625 (architecture-9)

Suggested renames:

• sanitize_error_report — emphasizes that sanitization is primary purpose
• render_error_at_boundary — emphasizes it is the boundary choke-point
• Other options welcome

Acceptance Criteria:

• Decide on new name
• Update function and all call sites
• Update rustdoc to clarify this is the CWE-150 sanitization choke-point
• Review PR fix: harden terminal-escape rendering across all MdsError variants (CWE-150) #253 to understand why this boundary was chosen (relates to PF-004)

Note: This rename happened in the original review, but is now deferred as a follow-up naming fix. Current name works; rename improves clarity only.