fix(ci): authenticate tramiton-core fetch in the agent image build (main deploys)

The PR `check` job configures git auth for the private tramiton-core dependency,
but the main-branch `deploy-agent` job builds `Dockerfile.agent` where cargo also
fetches tramiton-core — inside the image build, with no credentials — so agent
image builds on main failed.

Inject the PAT as a BuildKit secret (never baked into a layer):
- Dockerfile.agent: `RUN --mount=type=secret,id=tramiton_token` configures the
  same https-insteadOf rewrite + CARGO_NET_GIT_FETCH_WITH_CLI before cargo build.
- deploy-agent: `DOCKER_BUILDKIT=1 docker build --secret id=tramiton_token,env=
  TRAMITON_FETCH_TOKEN ...`, reusing the existing TRAMITON_FETCH_TOKEN secret.

Only the agent image depends on tramiton-core; dashboard/mcp/docs builds are
unaffected. Self-tests on merge (deploy-agent runs when Dockerfile.agent changes).

Refs #118.

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

.gitea/workflows/ci.yml

@@ -191,13 +191,18 @@ jobs:
       image: docker:27-cli
     steps:
       - name: Build, push and trigger orca redeploy
+        env:
+          # PAT for fetching the private tramiton-core git dependency during the
+          # image build (injected as a BuildKit secret, never baked into a layer).
+          TRAMITON_FETCH_TOKEN: ${{ secrets.TRAMITON_FETCH_TOKEN }}
         run: |
           apk add --no-cache git curl openssl
           git init && git remote add origin "${GITHUB_SERVER_URL}/${GITHUB_REPOSITORY}.git"
           git fetch --depth=1 origin "${GITHUB_SHA}" && git checkout FETCH_HEAD
           IMAGE=registry.meghsakha.com/compliance-agent
           echo "${{ secrets.REGISTRY_PASSWORD }}" | docker login registry.meghsakha.com -u "${{ secrets.REGISTRY_USERNAME }}" --password-stdin
-          docker build -f Dockerfile.agent -t "$IMAGE:latest" -t "$IMAGE:${GITHUB_SHA}" .
+          DOCKER_BUILDKIT=1 docker build --secret id=tramiton_token,env=TRAMITON_FETCH_TOKEN \
+            -f Dockerfile.agent -t "$IMAGE:latest" -t "$IMAGE:${GITHUB_SHA}" .
           docker push "$IMAGE:latest" && docker push "$IMAGE:${GITHUB_SHA}"
           PAYLOAD=$(printf '{"ref":"refs/heads/main","repository":{"full_name":"sharang/compliance-scanner-agent"},"head_commit":{"id":"%s","message":"deploy agent"}}' "${GITHUB_SHA}")
           SIG=$(printf '%s' "$PAYLOAD" | openssl dgst -sha256 -hmac "${{ secrets.ORCA_WEBHOOK_SECRET }}" | awk '{print $2}')

Dockerfile.agent

@@ -2,7 +2,16 @@ FROM rust:1.94-bookworm AS builder
 
 WORKDIR /app
 COPY . .
-RUN cargo build --release -p compliance-agent
+# compliance-agent depends on the private tramiton-core git repo. Authenticate
+# the fetch with a PAT passed as a BuildKit secret (never baked into a layer).
+# Build with: DOCKER_BUILDKIT=1 docker build --secret id=tramiton_token,env=TRAMITON_FETCH_TOKEN ...
+RUN --mount=type=secret,id=tramiton_token \
+    if [ -s /run/secrets/tramiton_token ]; then \
+      git config --global \
+        url."https://sharang:$(cat /run/secrets/tramiton_token)@gitea.meghsakha.com/".insteadOf \
+        "ssh://git@gitea.meghsakha.com:22222/"; \
+    fi && \
+    CARGO_NET_GIT_FETCH_WITH_CLI=true cargo build --release -p compliance-agent
 
 FROM debian:bookworm-slim
 RUN apt-get update && apt-get install -y ca-certificates libssl3 git curl python3 python3-pip npm golang-go php-cli && rm -rf /var/lib/apt/lists/*