feat(marketplace): plugin marketplace data model + Go store — closes #249

[tayebmokni]

Summary

Lays the data-model + Go store-layer foundation for the community plugin
marketplace (#249). The marketplace UI itself is a separate, later issue;
this PR ships the durable schema and the typed read/write surface the
future UI (and any CLI/worker) will share.

Migrations 000018–000022 (+ down)

• 000018_plugin_listings: catalogue rows — slug UNIQUE, name, author
  FK to users, homepage, SPDX license, primary_category, status with
  CHECK draft|listed|delisted|banned. Partial index on category
  WHERE status='listed', partial index on author. Dedicated
  marketplace_touch_updated_at trigger.
• 000019_plugin_versions: per-listing artefact records — version,
  wasm_sha256 BYTEA(32 CHECK), manifest JSONB, optional signature_hex,
  published_at, deprecated_at. UNIQUE(listing_id, version). Indexes on
  (listing_id, published_at DESC) and on wasm_sha256.
• 000020_plugin_compat_matrix: composite PK (plugin_version_id,
  host_min, host_max) so a version can declare multiple disjoint
  ranges. tested BOOLEAN. Range CHECK host_min <= host_max.
• 000021_plugin_ratings: composite PK (plugin_version_id, user_id)
  — one rating per user per version (a v1 rating stays on v1 when
  v2 ships). SMALLINT stars CHECK 1..5. Compound index on
  (plugin_version_id, stars) for index-only AVG(stars).
• 000022_plugin_install_events: append-only telemetry, BIGSERIAL PK,
  TEXT host_id (privacy-respecting hashed signature), event_type CHECK
  installed|activated|uninstalled|errored. FKs ON DELETE SET NULL so
  events survive parent deletes. Partial index on errored events.

Every up has a matching down; round-trip is exercised under Docker.

Go package — packages/go/plugins/marketplace

• doc.go + types.go — sentinels (ErrNotFound, ErrAlreadyExists,
  ErrInvalidInput), typed enums (ListingStatus, InstallEventType
  with .Valid()), and the five row structs.
• store.go — umbrella Store, PgxQuerier interface (so callers can
  pass a pgx.Tx), SQLSTATE helpers translating 23505→ErrAlreadyExists
  and 23514→ErrInvalidInput.
• listings.go — Create/Get/GetBySlug/List/ListByCategory/Update/Delete.
  Update uses the COALESCE pattern (nil pointer = leave alone) so the
  SQL shape stays constant.
• versions.go — Publish computes SHA-256 of the supplied wasm bytes;
  the bytes are not stored, only the digest. Get, ListByListing,
  Deprecate.
• compat.go — Upsert (ON CONFLICT DO UPDATE on tested),
  ListByVersion.
• ratings.go — Submit (UPSERT, created_at preserved on re-rate),
  Aggregate (zero-valued Aggregate for empty versions, not
  ErrNotFound).
• events.go — RecordInstallEvent (append-only), CountByListing with
  a window=0 lifetime path.

Tests

testcontainers Postgres applying the full migration tree:

• 16 unit tests — validation guards (empty slug, out-of-range stars,
  bad enum), constructor panics, SQLSTATE detection.
• 15 integration tests — Listings create + slug uniqueness + category
  partial-index + trigger-driven updated_at + delete cascade,
  Versions publish + SHA-256 capture + duplicate→ErrAlreadyExists +
  Deprecate idempotency, Compat upsert + inverted-range rejection,
  Ratings avg+count + UPSERT preserving created_at + zero-rating
  case, Events monotonic id + window count, full migration
  up→down→up round-trip.

Test plan

• cd packages/go && go vet ./plugins/marketplace/... — clean
• cd packages/go && go test -race -count=1 -short ./plugins/marketplace/... — 16/16 unit pass, 15 integration skip cleanly
• cd packages/go && go test -race -count=1 ./plugins/marketplace/... — 31/31 pass (~40s under Docker)
• cd packages/go && go build ./... — full workspace builds, no regression

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