Establish canonical operator copy foundations

[cbusillo]

Summary

• record the accepted sample / comparison clips / computer phase language in the durable vocabulary policy
• centralize operator-facing file sizes on decimal units and convert inherited binary-unit copy truthfully
• add a shared operator-copy boundary for backend states and errors, then apply it to Other Studio, Activity, and evidence status helpers
• remove raw ISO timestamp fallback copy while preserving active-item paths and telemetry

Validation

• bash scripts/pre-commit-check.sh
• browser smoke: all desktop, narrow, workflow, and empty fixtures passed
• manual browser QA: Other Library, active Other Studio desktop/narrow, Activity, and Finished
• PyCharm changed-files inspection attempted; the helper reported mixed-scope semantic coverage missing plus broad pre-existing duplicate/style warnings, while Svelte check, ESLint, Prettier, tests, and build are clean

Closes #532
Refs #531