nomos+web: streaming, provider routing, event gap-fill, embedded UI; fix approval FK & session context

Agent (cmd/nomos):
- Stream LLM tokens via NewStreaming; emit text_delta then final text.
- OpenRouter provider routing: data_collection=deny (ZDR) + require_parameters;
  NOMOS_PROVIDER_SORT opt-in; Exacto via model suffix.
- Multi-turn: reload session history into context; UI passes session id.
- Fix agent_activity logging (agent_id/session_id) and mcpClient data race.

Events (live control-room feed):
- approval.created (mcp), approval.decided (api), execution.completed/failed
  (approved-action path), signal.raised/resolved + health.changed (scheduler,
  transition-gated).

Fixes:
- createApproval FK violation (reuse execution entity) — the agent's only
  write path; log the previously-swallowed errors.

Web UI:
- Embed web/dist via //go:embed (single binary); Dockerfile builds SPA into
  the Go stage; committed .gitkeep placeholder keeps backend-only builds green.
- Caddy: Authentik-gated /agent/* -> nomos so the UI reaches the agent
  same-origin in production.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

web/src/app.css

@@ -0,0 +1,62 @@
+:root {
+  --bg: #0d1117;
+  --bg-surface: #161b22;
+  --bg-deeper: #0a0e13;
+  --bg-hover: #21262d;
+  --bg-active: #292e36;
+  --border: #30363d;
+  --text: #e6edf3;
+  --text-muted: #8b949e;
+  --accent-blue: #58a6ff;
+  --accent-green: #3fb950;
+  --accent-red: #f85149;
+  --accent-orange: #d29922;
+  --font-mono: 'SF Mono', 'Fira Code', 'Cascadia Code', monospace;
+}
+
+*, *::before, *::after {
+  box-sizing: border-box;
+  margin: 0;
+  padding: 0;
+}
+
+html, body {
+  height: 100%;
+  background: var(--bg);
+  color: var(--text);
+  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
+  font-size: 14px;
+  line-height: 1.4;
+  -webkit-font-smoothing: antialiased;
+}
+
+#app {
+  height: 100%;
+}
+
+::-webkit-scrollbar {
+  width: 6px;
+  height: 6px;
+}
+
+::-webkit-scrollbar-track {
+  background: transparent;
+}
+
+::-webkit-scrollbar-thumb {
+  background: var(--border);
+  border-radius: 3px;
+}
+
+::-webkit-scrollbar-thumb:hover {
+  background: var(--text-muted);
+}
+
+a {
+  color: var(--accent-blue);
+  text-decoration: none;
+}
+
+a:hover {
+  text-decoration: underline;
+}