[v3.19 hub-assets] merge sin hub and sin assets into one tool catalog

[Delqhi]

Merge sin hub and sin assets into one tool catalog

sin-code hub list/search/info (v3.12.0) and sin assets list/validate/show/import (v3.17.0) are two CLIs for the same concept: a catalog of tools (agents, commands, skills). Two CLIs for one concept is UX-confusion.

Why

Operators don't think "do I want the hub or the assets?" They think "do I have a tool for this?" The answer should be one command.

What ships

Single CLI: sin catalog

sin catalog list                    # all assets (hub + vendored)
sin catalog list --kind=agent       # filter by kind
sin catalog search "go reviewer"    # across both sources
sin catalog info agent go-reviewer  # show one
sin catalog import --source ./vendor/ecc  # import vendored assets
sin catalog sync                     # refresh from all sources

Source abstraction

Both internal/hub/ and internal/assets/ produce *Asset-shaped data (or a similar type). A common Source interface:

type Source interface {
    Name() string                              // "vendored", "hub", "remote"
    List(ctx context.Context) ([]*Asset, error)
    Search(ctx context.Context, q string) ([]*Asset, error)
    Get(ctx context.Context, name string) (*Asset, error)
}

The CLI walks all sources, merges results, de-dupes by (kind, name).

Deprecation

sin hub and sin assets remain as deprecated aliases of sin catalog for one minor release. After v3.20, they go.

Acceptance criteria

• sin catalog list shows the union of both sources, de-duped
• sin catalog search ranks across both sources
• The Source interface has a reference implementation for each existing source (vendored + hub)
• The deprecation warnings are visible (printed to stderr, not silent)
• Test coverage ≥ 80%

Mandates

• M5 (module path): no new module; new code in cmd/sin-code/internal/catalog/
• M6 (SIN tools over naive built-ins): the catalog uses the existing Selector (from PR feat: continuous-learning + lifecycle-hooks + asset-loader + eval-driven-dev + PRP workflow #144) for ranking

Related

• cmd/sin-code/internal/hub/ — the v3.12.0 hub subsystem
• cmd/sin-code/internal/assets/ — the v3.17.0 asset loader + selector
• docs/EVAL-HARNESS.md and docs/INSTINCTS.md — both reference the catalog

Estimated scope

~3-4 days, 1 PR. Mostly refactoring; the pieces exist, they just need to be unified.

[Delqhi]

Closed: shipped in PR #208 (feat(catalog): sin-code catalog CLI + Source interface, issue #163 hub-assets merge). The internal/catalog/ package with HubSource + AssetsSource adapters + sin-code catalog CLI are live on main. 21 race-clean tests. sin-code hub continues to work (deprecation plan documented in catalog.doc.md).