fix: correct stale counts across all docs (tables 19→21, MCP tools 76→78, tests 860→900+)

V2 audit found 3 critical number mismatches propagated across 8 files:
- Table count was 19 everywhere but actual migrations create 21 tables
- MCP tool count was 76 but tools.go registers 78 (M21/M22 additions)
- README MCP breakdown claimed 83 tools with math summing to 90
- architecture.md still had stale 860+ test count
- features.md OpenAPI claim said 93 ops but spec has 78
- mcp.md tool-per-domain table had wrong counts in 10 of 16 rows
- Added 3 network_scan_targets to seed_demo.sql for demo completeness
- Added curl examples to Agent Groups section in features.md

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

migrations/seed_demo.sql

@@ -201,6 +201,13 @@ INSERT INTO agent_groups (id, name, description, match_os, match_architecture, m
   ('ag-manual',       'Manual Group',        'Manually managed agent group (no dynamic criteria)', '', '',   '',              '',      false, NOW(), NOW())
 ON CONFLICT (id) DO NOTHING;
 
+-- Network Scan Targets
+INSERT INTO network_scan_targets (id, name, cidrs, ports, enabled, scan_interval_hours, timeout_ms, created_at, updated_at) VALUES
+  ('nst-dc1-web',  'DC1 Web Servers',     '{10.0.1.0/24}',              '{443,8443}',  true,  6, 5000, NOW(), NOW()),
+  ('nst-dc2-apps', 'DC2 Application Tier', '{10.0.2.0/24,10.0.3.0/24}', '{443}',       true,  6, 5000, NOW(), NOW()),
+  ('nst-dmz',      'DMZ Public Endpoints', '{192.168.100.0/24}',         '{443,8443,9443}', true, 12, 3000, NOW(), NOW())
+ON CONFLICT (id) DO NOTHING;
+
 -- Agent Group Members (manual membership for the manual group)
 INSERT INTO agent_group_members (agent_group_id, agent_id, membership_type, created_at) VALUES
   ('ag-manual', 'ag-web-prod',    'include', NOW()),