docs: restructure SCOPE.md as shipped inventory vs product boundary

Rewrite SCOPE to separate what issue-core provides today (models, backends,
CLI, REST, sync, deploy) from in-scope growth and out-of-scope fleet work.
Align package __init__ description with the connector role.

issue_core/__init__.py

@@ -1,24 +1,16 @@
 """
-issue-core — Authoritative Task Lifecycle Manager
+issue-core — external issue-tracker connector
 
-The single observable place in the Coulomb org where tasks land —
-regardless of whether they were created by a human, by activity-core,
-or by an agent. Backend-agnostic via a plugin architecture.
+Backend-agnostic CLI, library, and optional REST surface for operating on
+third-party issue trackers (Gitea/Forgejo, local SQLite). Not the origin of
+fleet work records (see INTENT.md / SCOPE.md).
 
-Features:
-- Unified issue model across all backends
-- Plugin-based backend architecture
-- Local SQLite backend for offline work
-- Bidirectional synchronization
-- CLI-first interface
-- REST ingestion endpoint for activity-core's IssueSink
-
-Supported Backends:
-- Local SQLite (offline/standalone)
-- Gitea (GitHub-compatible API)
-- Future: GitHub, GitLab, JIRA, Redmine
+Shipped:
+- Unified issue model and IssueBackend plugin architecture
+- Local SQLite + Gitea backends; bidirectional sync CLI
+- CLI (`issue` / `issue-core`) and optional FastAPI REST (`issue serve`)
 """
 
 __version__ = "0.2.1"
 __author__ = "Coulomb / MarkiTect Project"
-__description__ = "Authoritative task lifecycle manager with plugin architecture"
+__description__ = "External issue-tracker connector with plugin backends"