Implement State Hub v0.2: dependency graph, next-steps suggestions, design boundary

S0 — Design boundary formalised across all integration surfaces:
- TOOLS.md restructured with Design Boundary section, Sanctioned Write Tools,
  and Bootstrap-Only Tools (create_workstream, create_task) with explicit note
- project_claude_md.template and railiance CLAUDE.md updated with boundary note
  and get_next_steps() in session start protocol
- Global ~/.claude/CLAUDE.md updated accordingly

S1 — Workstream dependency graph:
- WorkstreamDependency model (directed edge, CASCADE on delete, unique pair constraint)
- Alembic migration 0b547c153153; script.py.mako added (was missing)
- REST API: POST/GET /workstreams/{id}/dependencies/, DELETE …/{dep_id} (hard delete)
- StateSummary open_workstreams enriched with depends_on/blocks lists
- MCP tools: create_dependency(), list_dependencies()
- Dashboard workstreams page: Dependencies section with relationship cards
- Seeded: custodian-agent-runtime → llm-shared-library + phase-0-operational-baseline

S2 — Suggesting Next Steps (sanctioned write use case #2):
- GET /state/next_steps derives suggestions from recently resolved decisions
  (→ first open task in same workstream) and cleared dependencies
  (→ first todo task in now-unblocked workstream)
- StateSummary.next_steps included on every summary call
- MCP tool: get_next_steps()
- Dashboard: "What's next?" card grid above Registered Projects

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

api/main.py

@@ -4,7 +4,7 @@ from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
 
 from api.database import engine
-from api.routers import decisions, progress, state, tasks, topics, workstreams
+from api.routers import decisions, progress, state, tasks, topics, workstreams, workstream_dependencies
 
 
 @asynccontextmanager
@@ -23,12 +23,13 @@ app = FastAPI(
 app.add_middleware(
     CORSMiddleware,
     allow_origins=["http://localhost:3000", "http://127.0.0.1:3000"],
-    allow_methods=["GET", "POST", "PATCH"],
+    allow_methods=["GET", "POST", "PATCH", "DELETE"],
     allow_headers=["Content-Type"],
 )
 
 app.include_router(topics.router)
 app.include_router(workstreams.router)
+app.include_router(workstream_dependencies.router)
 app.include_router(tasks.router)
 app.include_router(decisions.router)
 app.include_router(progress.router)