Finish update-profile file-helper adoption

[codeforester]

Problem

cli/bash/commands/basectl/subcommands/update_profile.sh imports file/lib_file.sh but still carries local section-content comparison and manual temp-file cleanup around behavior that is close to the shared file helper surface.

Examples:

• base_update_profile_update_file_needs_change creates current and desired temp files, compares them, and manually removes them.
• Profile config writes still use ad hoc target-temp handling.

Scope

• Reuse existing base-bash-libs file/temp helpers where they already cover the behavior.
• If a very small helper is missing from file/lib_file.sh, define the companion base-bash-libs change before replacing Base code.
• Preserve basectl update-profile, --remove, --defaults, and dry-run behavior.

Acceptance Criteria

• update_profile.sh has less local temp/section-comparison plumbing.
• Managed shell profile updates remain stable.
• Focused update-profile tests and ShellCheck pass.