fix(ci): restore refactor workflow parity

.github/harness/Dockerfile

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+FROM public.ecr.aws/docker/library/python:3.12-slim
+
+# Install system dependencies
+RUN apt-get update && apt-get install -y \
+    git \
+    curl \
+    jq \
+    && rm -rf /var/lib/apt/lists/*
+
+# The clone token is baked into the image. This image must be treated as a secret
+# and stored only in a registry with equivalent access controls.
+ARG CLONE_TOKEN
+
+# Configure git to use clone token for HTTPS clones
+RUN git config --global url."https://${CLONE_TOKEN}@github.com/".insteadOf "https://github.com/"
+
+WORKDIR /opt/workspace

.github/harness/README.md

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+# Harness Resources
+
+Container and scripts for AI-powered automation via
+[AgentCore Harness](https://docs.aws.amazon.com/bedrock/latest/userguide/agentcore.html).
+
+## Structure
+
+```
+harness/
+|-- Dockerfile            # Container image for the harness runtime
+|-- harness_review.py     # Invokes the harness to review PRs (SigV4 + event stream)
+`-- prompts/
+    |-- system.md         # System prompt (workspace context)
+    `-- review.md         # PR review task prompt
+```
+
+## Current: PR Reviewer
+
+Reviews pull requests on open/reopen via `.github/workflows/pr-ai-review.yml`.
+
+### Authentication
+
+The Dockerfile takes one build arg:
+
+- **`CLONE_TOKEN`** - baked into git config for cloning private repos
+
+The workflow-side review script uses its short-lived **`GITHUB_TOKEN`** to read
+existing PR discussion and submit the Harness result. The token is never sent
+to the Harness runtime or persisted in the Harness image.
+
+### Building the container
+
+```bash
+finch build \
+  --build-arg CLONE_TOKEN=<pat-for-cloning> \
+  -t pr-reviewer .github/harness/
+```
+
+## Future: Tester
+
+This directory will also house a harness-based test runner.