fix(import): separate type advice from variant identity

[santosli]

Summary

• remove inferred User/Remote advice from Rust import variant identity while preserving snapshot, source, status, and conflict boundaries
• aggregate per-location type advice and require an explicit User/Remote choice when equivalent locations disagree
• update Import Review to show one general-video variant with four disclosed locations and submit only its primary source

Safety contract

• Rust remains authoritative for group, variant, location, snapshot, and primary identity
• materially different snapshots, statuses, or conflicts remain separate variants
• mixed type advice does not select a classification implicitly
• one request is emitted for the selected primary; equivalent locations remain review-only
• the core duplicate-name before-write guard remains unchanged

Verification

• cargo fmt --check
• cargo clippy --workspace --all-targets --all-features --locked -- -D warnings
• cargo test --offline (CLI 29, core 323, desktop Rust 10, git 41, GitHub parser 8)
• npm test (257/257)
• npm --workspace apps/desktop run build
• npm audit --audit-level=high (0 vulnerabilities)
• cargo audit (exit 0; 18 existing allowed warnings)
• git diff --check

Visual QA

• collapsed: /tmp/skillbox-import-mixed-collapsed.png
• expanded locations: /tmp/skillbox-import-mixed-expanded.png
• explicit Remote classification: /tmp/skillbox-import-mixed-classified.png
• 1000x760 narrow: /tmp/skillbox-import-mixed-narrow.png
• narrow document width equals viewport width (1000px); no horizontal overflow