Summary

Closes #91 — completes the project-scoping work (#83/#84/#92) so every evolution-dashboard panel reflects the selected project. Threads project through the file-based readers and adds a skill_attribution project column.

Changes

• paths.rs: resolve_harness_dir(project) + _for(project) helpers for seesaw/variants/evolved/manifests.
• seesaw/variants/snapshot: load_registry_for(project), VariantPool::load_for(project), build_snapshot_for(project) (existing no-arg fns delegate to _for(None), preserving all current callers).
• snapshot metrics_summary_for(project) uses the scoped loader (load_metrics_scoped_pool).
• serve.rs: 4 arms (get_seesaw_registry/get_variant_pool/get_harness_snapshot/get_manifests) pass project through.
• skill_attribution: composite PK (skill_name, project) via idempotent table-rebuild migration (_harness_meta.skill_attribution_pk_v2); writer binds project with ON CONFLICT (skill_name, project); scoped load_metrics_scoped_pool filters WHERE project = ?.

Acceptance Criteria

• AC1 ✅ switching project changes seesaw/variants/snapshot/manifests data (readers now project-aware).
• AC2 ✅ skill_attribution migration idempotent + scoped (no more "no such column: project").
• AC3 ✅ cargo test --lib 646 passed; cargo clippy --all-targets -- -D warnings clean; cargo fmt --check clean.

Test Plan

• cargo test --lib: 646 passed
• clippy --all-targets -D warnings: clean
• cargo fmt --check: clean
• CI green