feat(0130): kanban_cpp v2 — backend Go + 5 registry parser fns + epic/sub-issues

Registry (issue 0130a):
- 5 fns infra: parse_issue_md, write_issue_md, scan_issues_dir,
  scan_flows_dir, watch_dir_fsnotify
- 3 tipos: Issue, Flow, FsEvent
- Tests round-trip + scan reales + watcher fsnotify (all PASS)
- Capability group 'kanban' nuevo (docs/capabilities/kanban.md)

Apps:
- apps/kanban_cpp/ (sub-repo) — frontend ImGui: board drag-drop,
  flows, filters, detail con CSV editors
- apps/kanban_cpp/backend/ — Go service port 8487: REST + SSE +
  fsnotify watcher, parser bidireccional MD<->SQLite cache

Issues:
- dev/issues/0130-kanban-cpp-v2.md (epic)
- 0130a parser, 0130b backend, 0130c frontend

CMakeLists.txt: add_subdirectory apps/kanban_cpp (registrado por
init_cpp_app scaffolder).

End-to-end verde: backend devuelve 189 issues + 9 flows; PATCH a
/api/issues/{id} reescribe .md (solo frontmatter, body intacto);
frontend --self-test exit 0; tests Go infra 5/5 PASS.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

dev/issues/0130b-kanban-cpp-v2-backend.md

@@ -0,0 +1,114 @@
+---
+id: "0130b"
+title: "Backend Go kanban_cpp v2: schema + handlers + watcher + SSE"
+status: pendiente
+type: app
+domain:
+  - apps-infra
+  - dev-ux
+scope: app-scoped
+priority: alta
+depends:
+  - "0130a"
+blocks:
+  - "0130c"
+related:
+  - "0130"
+created: 2026-05-22
+updated: 2026-05-22
+tags: [service, kanban, go, sqlite, sse]
+flow: "0130"
+---
+
+# 0130b — Backend Go kanban_cpp v2
+
+**Status:** pendiente
+
+## Por que
+
+Servicio HTTP local que sirve los issues + flows del proyecto al frontend C++. Es un wrapper fino sobre las funciones del registry de 0130a + SQLite cache + watcher.
+
+## Estructura
+
+```
+apps/kanban_cpp/backend/
+  app.md                  # tag service
+  go.mod
+  main.go                 # entry: flags + run
+  db.go                   # open + apply migrations + upsert helpers
+  handlers.go             # endpoints REST
+  sse_hub.go              # broadcaster
+  watcher.go              # bind a watch_dir_fsnotify + re-ingesta + emit SSE
+  ingest.go               # scan → upsert; usa 0130a
+  migrations/
+    001_init.sql
+  operations.db           # creada en runtime
+```
+
+## Endpoints
+
+| Verbo | Path | Notas |
+|---|---|---|
+| GET | `/api/health` | `{ok:true, version, count_issues, count_flows}` |
+| GET | `/api/issues` | filtros: `status`, `domain`, `priority`, `tag`, `scope` |
+| GET | `/api/issues/{id}` | issue + body |
+| PATCH | `/api/issues/{id}` | partial update frontmatter → `write_issue_md` + re-ingesta + SSE |
+| GET | `/api/flows` | filtros: `status`, `kind` |
+| GET | `/api/flows/{id}` | flow + body |
+| GET | `/api/meta` | enums leidos de `dev/TAXONOMY.md` |
+| GET | `/api/sse` | stream `{type, id, path}` |
+
+CORS abierto local (`*`). Logger middleware.
+
+## Schema (migrations/001_init.sql)
+
+```sql
+CREATE TABLE IF NOT EXISTS issues (
+    id           TEXT PRIMARY KEY,
+    title        TEXT NOT NULL,
+    status       TEXT NOT NULL,
+    type         TEXT,
+    scope        TEXT,
+    priority     TEXT,
+    domain_json  TEXT NOT NULL DEFAULT '[]',
+    tags_json    TEXT NOT NULL DEFAULT '[]',
+    depends_json TEXT NOT NULL DEFAULT '[]',
+    blocks_json  TEXT NOT NULL DEFAULT '[]',
+    related_json TEXT NOT NULL DEFAULT '[]',
+    flow_id      TEXT,
+    body         TEXT NOT NULL DEFAULT '',
+    file_path    TEXT NOT NULL,
+    mtime_ns     INTEGER NOT NULL,
+    created_at   TEXT,
+    updated_at   TEXT,
+    completed    INTEGER NOT NULL DEFAULT 0  -- 1 si vive en completed/
+);
+CREATE INDEX IF NOT EXISTS idx_issues_status ON issues(status);
+CREATE INDEX IF NOT EXISTS idx_issues_priority ON issues(priority);
+
+CREATE TABLE IF NOT EXISTS flows (
+    id           TEXT PRIMARY KEY,
+    title        TEXT NOT NULL,
+    status       TEXT,
+    kind         TEXT,
+    tags_json    TEXT NOT NULL DEFAULT '[]',
+    body         TEXT NOT NULL DEFAULT '',
+    file_path    TEXT NOT NULL,
+    mtime_ns     INTEGER NOT NULL
+);
+```
+
+## DoD
+
+- `curl http://localhost:8487/api/health` devuelve 200 + counts.
+- `curl http://localhost:8487/api/issues | jq 'length' >= 90`.
+- `curl -X PATCH /api/issues/0130 -d '{"status":"in-progress"}'` reescribe `dev/issues/0130-*.md` (status updated, body intacto).
+- Despues del PATCH, suscriptor SSE recibe evento `{type:"updated", id:"0130"}`.
+- Tras `mv dev/issues/0130-*.md dev/issues/completed/`, watcher actualiza fila (`completed=1`).
+- `go test ./...` verde.
+
+## Anti-scope
+
+- No expone proposals ni capabilities (eso es MCP registry).
+- No autentica (local-only por ahora).
+- No persiste estado UI (eso lo hace el frontend).