refactor: unify eprint_error settle patterns in watch.rs

[dean0x]

Location: crates/mds-cli/src/watch.rs:869, :877

What: eprint_error + error-settle pattern is repeated in two identical pairs across watch.rs. The pairs at :869/:877 and :1280/:1292 are identical but sit in different arms of nested match expressions.

Why deferred: Refactoring requires restructuring match logic, which is out of scope for the security hardening PR #253. Better approached as a dedicated refactor.

Source review: .devflow/docs/reviews/fix-esc-injection-176/2026-07-25_1625 (complexity-7)

Acceptance Criteria:

• Identify all duplicate error-settle patterns in watch.rs
• Extract common helper if refactoring is feasible
• Verify no behavior change in file watching

Note: Two identical pairs exist but extracting requires restructuring nested match expressions. Evaluate trade-off before proceeding.