feat: rename to issue-core and add task ingestion endpoint

Renames the package, distribution, CLI alias, Makefile targets, and
working directory from issue-facade to issue-core, signalling its
role as the authoritative task lifecycle manager for the Coulomb org
(peer to activity-core, rules-core, project-core).

Adds POST /issues/ ingestion endpoint for activity-core's IssueSink,
under a new optional [api] extra. The endpoint is served by `issue
serve`, authenticates via the ISSUE_CORE_API_KEY env var (Bearer or
X-API-Key header), and routes the TaskSpec payload to the configured
default backend with full traceability metadata embedded in
sync_metadata.

- T01: Python package issue_tracker -> issue_core, dir rename
- T02: registered in state hub under custodian domain
- T03: INTENT.md (what it is, what it isn't, how it fits)
- T04: SCOPE.md (in/out-of-scope, integration boundaries)
- T05: POST /issues/ via FastAPI + Uvicorn, 9 unit tests
- T06: docs/nats-task-ingestion.md design stub

Closes ISSC-WP-0001.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

AGENT_INTEGRATION.md

@@ -1,10 +1,10 @@
 # Agent Integration Guide
 
-**Issue Facade for Autonomous Coding Agent Coordination**
+**Issue Core for Autonomous Coding Agent Coordination**
 
 ## Purpose
 
-The **Issue Facade** capability provides a standardized interface for autonomous coding agents to coordinate project implementation through issue tracking. Instead of agents directly interfacing with platform-specific APIs (GitHub, GitLab, Gitea), they use a unified abstraction that works consistently across backends.
+The **Issue Core** capability provides a standardized interface for autonomous coding agents to coordinate project implementation through issue tracking. Instead of agents directly interfacing with platform-specific APIs (GitHub, GitLab, Gitea), they use a unified abstraction that works consistently across backends.
 
 ### Why Issue Tracking for Agent Coordination?
 
@@ -67,7 +67,7 @@ Issue tracking provides a natural coordination mechanism for multi-agent softwar
 ### 1. Installation
 
 ```bash
-cd capabilities/issue-facade
+cd capabilities/issue-core
 pip install -e .
 ```
 
@@ -99,7 +99,7 @@ issue backend set-default my-project
 # Configure local SQLite backend
 issue backend add local-work local
 # Prompts for:
-# - Database path: .issue-facade/issues.db
+# - Database path: .issue-core/issues.db
 
 issue backend set-default local-work
 ```
@@ -178,8 +178,8 @@ issue list --label=reviewed --state=closed --format=json | \
 
 ```python
 # Agent creates implementation issues from requirements
-from issue_tracker.backends.gitea import GiteaBackend
-from issue_tracker.core.models import Issue, Label, IssueState
+from issue_core.backends.gitea import GiteaBackend
+from issue_core.core.models import Issue, Label, IssueState
 from datetime import datetime, timezone
 
 backend = GiteaBackend()
@@ -224,9 +224,9 @@ for task in subtasks:
 ### Python Integration
 
 ```python
-from issue_tracker.backends.gitea import GiteaBackend
-from issue_tracker.core.models import Issue, Label, IssueState, User
-from issue_tracker.core.interfaces import IssueFilter
+from issue_core.backends.gitea import GiteaBackend
+from issue_core.core.models import Issue, Label, IssueState, User
+from issue_core.core.interfaces import IssueFilter
 from datetime import datetime, timezone
 import os
 
@@ -271,7 +271,7 @@ created.state = IssueState.IN_PROGRESS
 backend.update_issue(created)
 
 # Add comment
-from issue_tracker.core.models import Comment
+from issue_core.core.models import Comment
 comment = Comment(
     id=None,
     body="Analysis complete. Root cause: unclosed file handles in line 234",
@@ -432,7 +432,7 @@ issue sync push backup gitea-remote
 
 ```python
 # Check for conflicts before sync
-from issue_tracker.cli.sync_commands import sync_pull
+from issue_core.cli.sync_commands import sync_pull
 
 try:
     sync_pull(source='remote', target='local', dry_run=True)
@@ -505,7 +505,7 @@ Create a setup script for each project:
 #!/bin/bash
 # setup-issue-tracking.sh
 
-cat > .issue-facade-config << EOF
+cat > .issue-core-config << EOF
 GITEA_URL=https://gitea.example.com
 GITEA_OWNER=myorg
 GITEA_REPO=myproject
@@ -513,7 +513,7 @@ GITEA_TOKEN_FILE=~/.secrets/gitea-token
 EOF
 
 # Load config and configure backend
-source .issue-facade-config
+source .issue-core-config
 export GITEA_API_TOKEN=$(cat $GITEA_TOKEN_FILE)
 
 issue backend add $(basename $(pwd)) gitea <<INPUT
@@ -551,7 +551,7 @@ for issue_number in [1, 2, 3, 4, 5]:
     backend.update_issue(issue)
 
 # GOOD: Use local backend for bulk operations
-from issue_tracker.backends.local import LocalSQLiteBackend
+from issue_core.backends.local import LocalSQLiteBackend
 
 local = LocalSQLiteBackend()
 local.connect({'db_path': '/tmp/batch.db'})
@@ -595,7 +595,7 @@ if time.time() - last_fetch > 60:
 ### Phase 1: Auto-Configuration (v1.1)
 - Automatic git remote detection
 - Environment-variable-only setup
-- Per-repository `.issue-facade/config.json` support
+- Per-repository `.issue-core/config.json` support
 - `issue config detect` command
 
 ### Phase 2: Agent Features (v1.2)