Document zero-restart UI dev workflow in AGENTS.md

Add "Local UI Development" section with instructions for using the
docker-compose.dev-ui.yml override. Agents working on UI changes
should use this to avoid the slow volume-copy + restart cycle.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/Web/StellaOps.Web/AGENTS.md

@@ -27,9 +27,36 @@ Design and build the StellaOps web user experience that surfaces backend capabil
 - Branding uses Authority `/console/branding` and applies only whitelisted CSS variables.
 
 ## Key Paths
-- `src/Web/StellaOps.Web` ??? Angular workspace (to be scaffolded).
-- `docs/` ??? UX specs and mockups (to be added).
-- `ops/` ??? Web deployment manifests for air-gapped environments (future).
+- `src/Web/StellaOps.Web` — Angular workspace.
+- `docs/` — UX specs and mockups.
+- `devops/compose/docker-compose.dev-ui.yml` — Dev override for zero-restart UI development.
+
+## Local UI Development (IMPORTANT)
+
+For UI work against the Docker stack, **use the dev-ui compose override** to avoid
+restarting the gateway container after every build:
+
+```bash
+# One-time: apply the override (bind-mounts dist/ into the gateway)
+cd devops/compose
+docker compose -f docker-compose.stella-ops.yml -f docker-compose.dev-ui.yml up -d router-gateway
+
+# Build (output goes directly to gateway's wwwroot — no copy, no restart)
+cd src/Web/StellaOps.Web
+npx ng build --configuration=development
+
+# Or use watch mode for continuous rebuilds:
+npx ng build --configuration=development --watch
+```
+
+After build, just **refresh the browser** — the gateway serves the new files immediately.
+
+**Without the override**, you must copy files into the Docker volume and restart:
+```bash
+docker run --rm -v compose_console-dist:/output -v "...browser:/src:ro" alpine cp -a /src/. /output/
+docker restart stellaops-router-gateway
+```
+This is slow and should only be used for CI/production builds.
 
 ## Reachability Drift UI (Sprint 3600)