docs: move golem15.user to sm-user-plugin and supersede the Phase 1 extraction deferral

- new note .planning/notes/core-plugins-own-repos.md: shared core plugins live in sm-<name>-plugin repos mounted as submodules
- 01-CONTEXT deferral points to the note; PROJECT constraint and Key Decisions row
- ROADMAP Phase 12 repos and the 12-01 entry, and Phase 12 plans 12-01, 12-02, 12-05 name sm-user-plugin and the submodule commit workflow

.planning/PROJECT.md

@@ -134,7 +134,7 @@ Quality
 - **Compatibility**: `vue-fonoteka-app` and `fonoteka-mcp` must run unchanged; the Nuxt app's requests define the contract and response shapes are not improved during the port
 - **Realtime**: keep the Centrifugo server and port only the publisher and token issuing — the Nuxt client connects to Centrifugo directly
 - **Plugins**: compiled at build time; no runtime plugin loading without a decision note
-- **Two repositories**: `summercms.go` is the framework only (the `summer` packages, the CLI, the admin SPA shell, the parity harness tooling) and knows nothing about Płytarium; `fonoteka.go`, a sibling directory in the meta repo, is the application: a go.work workspace holding the ported plugins (user, translate, feedback, sitemap, fonoteka) and the app binary; websockets is not a separate app plugin (D-16, Phase 11): the framework realtime package `lighthouse` plus fonoteka's `config/realtime.yaml`, channel authorizers, `lighthouse.Mount` call and `ws-api` bucket replace it, requiring the framework by module path with a local replace during development. Roadmap phases name which repo each plan writes to; planning docs stay in `summercms.go/.planning`
+- **Two repositories**: `summercms.go` is the framework only (the `summer` packages, the CLI, the admin SPA shell, the parity harness tooling) and knows nothing about Płytarium; `fonoteka.go`, a sibling directory in the meta repo, is the application: a go.work workspace holding the application plugins (fonoteka, translate, feedback, sitemap) and the app binary, and mounting shared core plugins from their own `sm-<name>-plugin` repos as git submodules (the user plugin is `sm-user-plugin`, module `git.golem15.com/golem15/sm-user-plugin`, at `plugins/golem15/user`; see `.planning/notes/core-plugins-own-repos.md`); websockets is not a separate app plugin (D-16, Phase 11): the framework realtime package `lighthouse` plus fonoteka's `config/realtime.yaml`, channel authorizers, `lighthouse.Mount` call and `ws-api` bucket replace it, requiring the framework by module path with a local replace during development. Roadmap phases name which repo each plan writes to; planning docs stay in `summercms.go/.planning`
 - **Workflow**: lean planning (few, large plans per phase), a plan-count checkpoint before PLAN.md files are written, unit tests as the last plan of every phase, `go vet` and `go test ./...` green at every commit
 - **Commits**: no co-author tags; one logical change per commit; planning docs and code in separate commits
 - **Core plugin contracts**: the PHP user, blog, pages and payment plugins are shared across many projects; the Go ports must preserve their contracts and the PHP originals are not changed as part of this project
@@ -161,6 +161,7 @@ Quality
 | Parity harness is a day-one workstream | Fixture recording needs only the running PHP backend; it is the acceptance mechanism for every port phase | ✓ Good (Phase 2, 2026-09-17: 154/154 PHP self-replay, Nuxt/MCP fixtures, testcontainers Go runner) |
 | WinterCMS websockets plugin dissolved into the framework `lighthouse` package (Phase 11 D-16) | Realtime is transport-neutral framework code (drivers, authorizer registry, broadcasts); the app only binds config, the collection/wishlist authorizers, the Mount call, the ws-api bucket and the Album binding, so a separate app plugin would be an empty shell | ✓ Good (Phase 11 plan 11-03) |
 | Framework and application in two repos from day one (`summercms.go`, `fonoteka.go`) | Retrofitting the split later is more disruptive; shared stack plugins can be extracted for keios.eu without touching the framework; the framework never imports an app | ✓ Good (Phase 3: fonoteka.go workspace, user + fonoteka plugins, app.Handler test seam) |
+| Shared core plugins live in their own `sm-<name>-plugin` repos, mounted into each application as git submodules (first: sm-user-plugin, module `git.golem15.com/golem15/sm-user-plugin`) | A second application (sm-summercmsio-app) exists and the Journal port is next; one copy per core plugin instead of forks; supersedes the Phase 1 keios.eu trigger (`.planning/notes/core-plugins-own-repos.md`) | ✓ Good (2026-10-02, quick 261002-esz) |
 
 ## Evolution