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>

.github/workflows/release.yml

@@ -57,6 +57,7 @@ jobs:
           platforms: ${{ matrix.platform }}
           build-args: |
             APP_VERSION=${{ env.VERSION }}
+            AI_AGENT_ROLES_CATALOG_URL=https://raw.githubusercontent.com/vvzvlad/gitmost/main/agent-roles-catalog
           outputs: type=image,name=${{ env.IMAGE }},push-by-digest=true,name-canonical=true,push=true
           cache-from: type=gha,scope=${{ matrix.suffix }}
           cache-to: type=gha,scope=${{ matrix.suffix }},mode=max,ignore-error=true
@@ -85,6 +86,7 @@ jobs:
           platforms: ${{ matrix.platform }}
           build-args: |
             APP_VERSION=${{ env.VERSION }}
+            AI_AGENT_ROLES_CATALOG_URL=https://raw.githubusercontent.com/vvzvlad/gitmost/main/agent-roles-catalog
           push: false
           tags: |
             ${{ env.IMAGE }}:latest