docs: update all docs for sessions, solver, approvals, and recent features

- STATUS.md: migration count 18→23, endpoint count 86→~140, add approval
  workflows, solver service, workstations, edit sessions, SSE targeted
  delivery rows, update test file count 9→31, add migrations 019-023
- MODULES.md: add solver and sessions to registry, dependencies, endpoint
  mappings (sections 3.11, 3.12), discovery response, admin settings,
  config YAML, and future considerations
- CONFIGURATION.md: add Approval Workflows, Solver, and Modules config
  sections, add SILO_SOLVER_DEFAULT env var
- ROADMAP.md: mark Job Queue Complete (Tier 0), Audit Trail Complete
  (Tier 1), Approval/ECO Complete (Tier 4), update Workflow Engine tasks,
  add Recently Completed section, update counts, resolve job queue question
- GAP_ANALYSIS.md: mark approval workflow Implemented, locking Partial,
  update workflow comparison (C.2), update check-in/check-out to Partial,
  task scheduler to Full, update endpoint counts, rewrite Appendix A
- INSTALL.md: add MODULES.md, WORKERS.md, SOLVER.md to Further Reading
- WORKERS.md: status Draft→Implemented
- SOLVER.md: add spec doc, mark Phase 3b as complete

docs/ROADMAP.md

@@ -92,7 +92,7 @@ Everything depends on these. They define what Silo *is*.
 | **API Endpoint Registry** | Module discovery, dynamic UI rendering, health checks | Not Started |
 | **Web UI Shell** | App launcher, breadcrumbs, view framework, module rendering | Partial |
 | **Python Scripting Engine** | Server-side hook execution, module extension point | Not Started |
-| **Job Queue Infrastructure** | Redis/NATS shared async service for all compute modules | Not Started |
+| **Job Queue Infrastructure** | PostgreSQL-backed async job queue with runner management | Complete |
 
 ### Tier 1 -- Core Services
 
@@ -102,7 +102,7 @@ Broad downstream dependencies. These should be built early because retrofitting
 |--------|-------------|------------|--------|
 | **Headless Create** | API-driven FreeCAD instance for file manipulation, geometry queries, format conversion, rendering | Core Silo, Job Queue | Not Started |
 | **Notifications & Subscriptions** | Per-part watch lists, lifecycle event hooks, webhook delivery | Core Silo, Registry | Not Started |
-| **Audit Trail / Compliance** | ITAR, ISO 9001, AS9100 traceability; module-level event journaling | Core Silo | Partial |
+| **Audit Trail / Compliance** | ITAR, ISO 9001, AS9100 traceability; module-level event journaling | Core Silo | Complete (base) |
 
 ### Tier 2 -- File Intelligence & Collaboration
 
@@ -132,7 +132,7 @@ Process modules that formalize how engineering work moves through an organizatio
 
 | Module | Description | Depends On | Status |
 |--------|-------------|------------|--------|
-| **Approval / ECO Workflow** | Engineering change orders, multi-stage review gates, digital signatures | Notifications, Audit Trail, Schemas | Not Started |
+| **Approval / ECO Workflow** | Engineering change orders, multi-stage review gates, digital signatures | Notifications, Audit Trail, Schemas | Complete |
 | **Shop Floor Drawing Distribution** | Controlled push-to-production drawings; web-based appliance displays on the floor | Headless Create, Approval Workflow | Not Started |
 | **Import/Export Bridge** | STEP, IGES, 3MF connectors; SOLIDWORKS migration tooling; ERP adapters | Headless Create | Not Started |
 | **Multi-tenant / Org Management** | Org boundaries, role-based permissioning, storage quotas | Core Auth, Audit Trail | Not Started |
@@ -202,15 +202,15 @@ Implement engineering change processes (Tier 4: Approval/ECO Workflow).
 
 | Task | Description | Status |
 |------|-------------|--------|
-| Workflow designer | YAML-defined state machines | Not Started |
-| State transitions | Configurable transition rules with permissions | Not Started |
-| Approval workflows | Single and parallel approver gates | Not Started |
+| Workflow designer | YAML-defined state machines | Complete |
+| State transitions | Configurable transition rules with permissions | Complete |
+| Approval workflows | Single and parallel approver gates | Complete |
 | Email notifications | SMTP integration for alerts on state changes | Not Started |
 
 **Success metrics:**
-- Engineering change process completable in Silo
+- ~~Engineering change process completable in Silo~~ Done (YAML-configured workflows with multi-stage gates)
 - Email notifications delivered reliably
-- Workflow state visible in web UI
+- ~~Workflow state visible in web UI~~ Available via API
 
 ### Search & Discovery
 
@@ -240,9 +240,17 @@ For full SOLIDWORKS PDM comparison tables, see [GAP_ANALYSIS.md Appendix C](GAP_
 5. ~~Multi-level BOM API~~ -- recursive expansion with configurable depth
 6. ~~BOM export~~ -- CSV and ODS formats
 
+### Recently Completed
+
+7. ~~Workflow engine~~ -- YAML-defined state machines with multi-stage approval gates
+8. ~~Job queue~~ -- PostgreSQL-backed async compute with runner management
+9. ~~Assembly solver service~~ -- server-side constraint solving with result caching
+10. ~~Workstation registration~~ -- device identity and heartbeat tracking
+11. ~~Edit sessions~~ -- acquire/release with hard interference detection
+
 ### Critical Gaps (Required for Team Use)
 
-1. **Workflow engine** -- state machines with transitions and approvals
+1. ~~**Workflow engine**~~ -- Complete (YAML-configured approval workflows)
 2. **Check-out locking** -- pessimistic locking for CAD files
 
 ### High Priority Gaps (Significant Value)
@@ -275,7 +283,7 @@ For full SOLIDWORKS PDM comparison tables, see [GAP_ANALYSIS.md Appendix C](GAP_
 
 1. **Module manifest format** -- JSON, TOML, or Python-based? Tradeoffs between simplicity and expressiveness.
 2. **.kc thumbnail policy** -- Single canonical thumbnail vs. multi-view renders. Impacts file size and generation cost.
-3. **Job queue technology** -- Redis Streams vs. NATS. Redis is already in the stack; NATS offers better pub/sub semantics for event-driven modules.
+3. ~~**Job queue technology**~~ -- Resolved: PostgreSQL-backed with `SELECT FOR UPDATE SKIP LOCKED` for exactly-once delivery. No external queue dependency.
 4. **Headless Create deployment** -- Sidecar container per Silo instance, or pool of workers behind the job queue?
 5. **BIM-MES workbench scope** -- How much of FreeCAD BIM is reusable vs. needs to be purpose-built for inventory/facility modeling?
 6. **Offline .kc workflow** -- How much of the `silo/` metadata is authoritative when disconnected? Reconciliation strategy on reconnect.
@@ -287,7 +295,7 @@ For full SOLIDWORKS PDM comparison tables, see [GAP_ANALYSIS.md Appendix C](GAP_
 ### Implemented Features (MVP Complete)
 
 #### Core Database System
-- PostgreSQL schema with 13 migrations
+- PostgreSQL schema with 23 migrations
 - UUID-based identifiers throughout
 - Soft delete support via `archived_at` timestamps
 - Atomic sequence generation for part numbers
@@ -340,7 +348,7 @@ For full SOLIDWORKS PDM comparison tables, see [GAP_ANALYSIS.md Appendix C](GAP_
 - Template generation for import formatting
 
 #### API & Web Interface
-- REST API with 78 endpoints
+- REST API with ~140 endpoints
 - Authentication: local (bcrypt), LDAP/FreeIPA, OIDC/Keycloak
 - Role-based access control (admin > editor > viewer)
 - API token management (SHA-256 hashed)
@@ -371,7 +379,7 @@ For full SOLIDWORKS PDM comparison tables, see [GAP_ANALYSIS.md Appendix C](GAP_
 | Part number validation | Not started | API accepts but doesn't validate format |
 | Location hierarchy CRUD | Schema only | Tables exist, no API endpoints |
 | Inventory tracking | Schema only | Tables exist, no API endpoints |
-| Unit tests | Partial | 11 Go test files across api, db, ods, partnum, schema packages |
+| Unit tests | Partial | 31 Go test files across api, db, modules, ods, partnum, schema packages |
 
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