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>

README.md

@@ -1,10 +1,10 @@
-# Issue Facade - Agent Coordination via Issue Tracking
+# Issue Core - Agent Coordination via Issue Tracking
 
 **A unified interface for autonomous coding agents to coordinate project implementation through issue tracking systems.**
 
 ## Purpose
 
-The **Issue Facade** provides a standardized abstraction layer for coding agents to interact with issue tracking backends (Gitea, GitHub, GitLab, local SQLite). Instead of each agent implementing platform-specific API integrations, they use one consistent interface that works across all backends.
+The **Issue Core** provides a standardized abstraction layer for coding agents to interact with issue tracking backends (Gitea, GitHub, GitLab, local SQLite). Instead of each agent implementing platform-specific API integrations, they use one consistent interface that works across all backends.
 
 ### Why Issue Tracking for Agent Coordination?
 
@@ -40,10 +40,25 @@ Issue tracking provides natural coordination primitives for multi-agent software
 ### Installation
 
 ```bash
-cd capabilities/issue-facade
-pip install -e .
+cd capabilities/issue-core
+pip install -e .                  # CLI only
+pip install -e ".[api]"           # CLI + REST ingestion server
 ```
 
+### REST Ingestion Server
+
+issue-core exposes `POST /issues/` for upstream emitters (primarily
+activity-core's `IssueSink`). Launch with:
+
+```bash
+export ISSUE_CORE_API_KEY="$(python -c 'import secrets; print(secrets.token_urlsafe(32))')"
+issue serve --host 0.0.0.0 --port 8765
+```
+
+Clients authenticate with `Authorization: Bearer <key>` or `X-API-Key: <key>`.
+See `SCOPE.md` "TaskSpec payload" for the request schema, or visit
+`http://<host>:<port>/docs` once the server is running for live OpenAPI docs.
+
 ### Configuration (One-Time Setup)
 
 **For Gitea-backed projects:**
@@ -67,7 +82,7 @@ issue backend test myproject
 
 ```bash
 issue backend add local-work local
-# Prompts for: database path (.issue-facade/issues.db)
+# Prompts for: database path (.issue-core/issues.db)
 
 issue backend set-default local-work
 ```
@@ -108,8 +123,8 @@ issue close 42 --comment="Ready for review"
 Quick example:
 
 ```python
-from issue_tracker.backends.gitea import GiteaBackend
-from issue_tracker.core.interfaces import IssueFilter
+from issue_core.backends.gitea import GiteaBackend
+from issue_core.core.interfaces import IssueFilter
 
 # Initialize
 backend = GiteaBackend()
@@ -281,20 +296,20 @@ make test-unit
 
 ```bash
 # Run linter
-make issue-facade-lint
+make issue-core-lint
 
 # Format code
-black issue_tracker/ tests/
+black issue_core/ tests/
 
 # Type check
-mypy issue_tracker/
+mypy issue_core/
 ```
 
 ### Project Structure
 
 ```
-issue-facade/
-├── issue_tracker/
+issue-core/
+├── issue_core/
 │   ├── core/              # Domain models and interfaces
 │   │   ├── models.py      # Issue, Label, User, etc.
 │   │   └── interfaces.py  # IssueBackend, SyncableBackend
@@ -351,7 +366,7 @@ issue-facade/
 
 ## Comparison with Platform CLIs
 
-| Feature | Issue Facade | gh (GitHub) | glab (GitLab) |
+| Feature | Issue Core | gh (GitHub) | glab (GitLab) |
 |---------|--------------|-------------|---------------|
 | Multi-backend support | ✅ Yes | ❌ GitHub only | ❌ GitLab only |
 | Offline capability | ✅ Local SQLite | ❌ No | ❌ No |
@@ -362,7 +377,7 @@ issue-facade/
 
 ## Contributing
 
-The Issue Facade is designed to be extensible:
+The Issue Core is designed to be extensible:
 
 **To add a new backend:**
 1. Implement the `IssueBackend` interface (see `core/interfaces.py`)