feat(state-hub): implement v0.5 — dynamic domains & multi-repo

Replaces the hardcoded 6-domain PostgreSQL ENUM with a first-class
`domains` DB table, and adds a `managed_repos` table for multi-repo
support per domain.

P1 — Domain as a DB entity:
- Migration b1c2d3e4f5a6: creates `domains` table, migrates topics.domain
  ENUM column to domain_id FK, drops the domain ENUM type
- Domain ORM model (api/models/domain.py) + Pydantic schemas
- Domain API router: GET/POST /domains/, GET/PATCH /domains/{slug}/,
  rename and archive endpoints with EP/TD cascade on rename
- Topic model updated: domain_id FK + @property domain_slug for
  backwards-compatible JSON serialization (field renamed domain → domain_slug)
- TopicCreate/TopicRead updated; seed.py rewritten to use FK lookup

P2 — Multi-repo support:
- ManagedRepo ORM model (api/models/managed_repo.py) + schemas
- Repo API router: GET/POST /repos/, GET/PATCH /repos/{slug}/, archive
- Makefile: add-domain, rename-domain, add-repo, list-repos targets
- register_project.sh: verify domain via /domains/ API + POST /repos/

P3 — MCP tools & live validation:
- 6 new MCP tools: list_domains, create_domain, rename_domain,
  archive_domain, list_domain_repos, register_repo
- EP/TD routers: replace hardcoded VALID_DOMAINS set with per-request
  DB lookup — returns 422 with list of valid slugs on unknown domain
- State summary: adds domains: list[DomainSummary] (slug, name,
  repo_count, active_workstream_count, ep_count, td_count)
- TOOLS.md updated with domain management section

P4 — Dashboard:
- New domains.md page with KPI row + domain cards + repo lists
- domains.json.py + repos.json.py data loaders
- Domains page added to observablehq.config.js nav
- workstreams.md, extensions.md, techdept.md: domain_slug fix +
  dynamic domain list loaded from /domains/ API (no longer hardcoded)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

api/models/topic.py

@@ -1,7 +1,7 @@
 import enum
 import uuid
 
-from sqlalchemy import Enum, String, Text
+from sqlalchemy import Enum, ForeignKey, String, Text
 from sqlalchemy.dialects.postgresql import UUID
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 
@@ -14,15 +14,6 @@ class TopicStatus(str, enum.Enum):
     archived = "archived"
 
 
-class Domain(str, enum.Enum):
-    custodian = "custodian"
-    railiance = "railiance"
-    markitect = "markitect"
-    coulomb_social = "coulomb_social"
-    personhood = "personhood"
-    foerster_capabilities = "foerster_capabilities"
-
-
 class Topic(Base, TimestampMixin):
     __tablename__ = "topics"
 
@@ -32,11 +23,19 @@ class Topic(Base, TimestampMixin):
     slug: Mapped[str] = mapped_column(String(100), unique=True, nullable=False, index=True)
     title: Mapped[str] = mapped_column(String(255), nullable=False)
     description: Mapped[str | None] = mapped_column(Text, nullable=True)
-    domain: Mapped[Domain] = mapped_column(Enum(Domain), nullable=False)
+    domain_id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True),
+        ForeignKey("domains.id", ondelete="RESTRICT"),
+        nullable=False,
+        index=True,
+    )
     status: Mapped[TopicStatus] = mapped_column(
         Enum(TopicStatus), nullable=False, default=TopicStatus.active
     )
 
+    domain: Mapped["Domain"] = relationship(  # noqa: F821
+        "Domain", back_populates="topics", lazy="selectin"
+    )
     workstreams: Mapped[list["Workstream"]] = relationship(  # noqa: F821
         "Workstream", back_populates="topic", lazy="selectin"
     )
@@ -46,3 +45,10 @@ class Topic(Base, TimestampMixin):
     progress_events: Mapped[list["ProgressEvent"]] = relationship(  # noqa: F821
         "ProgressEvent", back_populates="topic", lazy="selectin"
     )
+
+    @property
+    def domain_slug(self) -> str | None:
+        """Returns the domain slug string for serialization."""
+        if self.domain is not None:
+            return self.domain.slug
+        return None