refactor(ai-roles): bake catalog URL at image build, drop local-fs source

The agent-roles catalog source is no longer hardcoded in app code and no
longer supports a local filesystem directory. The provider now fetches only
from an http(s):// base URL read from AI_AGENT_ROLES_CATALOG_URL; an empty or
non-http value yields a 502 (catalog unavailable). The default URL is baked
into the Docker image at build time and set per branch in CI.

- provider: drop readLocal + node:fs/node:path; readRelative requires http(s)
  and 502s otherwise; remote fetch/streaming-cap/SSRF guards unchanged.
- environment.service: keep AI_AGENT_ROLES_CATALOG_URL (default ''); comment
  updated to reflect build-time injection, remote-only.
- Dockerfile: add ARG+ENV AI_AGENT_ROLES_CATALOG_URL in the installer stage.
- CI: develop.yml builds with the develop raw URL; release.yml (both build
  steps) with the main raw URL.
- tests: replace local-fixture tests with remote-mock happy/malformed bundle
  tests and a non-http => 502 case; path-traversal block uses an https source.
- docs: update .env.example, CHANGELOG (#222), agent-roles-catalog/README.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Dockerfile

@@ -23,6 +23,10 @@ RUN apt-get update \
 
 WORKDIR /app
 
+# Agent-roles catalog base URL, baked at build time (set per-branch in CI).
+ARG AI_AGENT_ROLES_CATALOG_URL=""
+ENV AI_AGENT_ROLES_CATALOG_URL=$AI_AGENT_ROLES_CATALOG_URL
+
 # Copy apps
 COPY --from=builder /app/apps/server/dist /app/apps/server/dist
 COPY --from=builder /app/apps/client/dist /app/apps/client/dist