Gadfly: agentic adversarial PR reviewer (initial extraction)

Standalone, Docker-packaged extraction of the agentic PR reviewer that runs in
Gitea Actions: reads the checked-out repo with read-only tools (read_file/grep/
find_files/get_diff), verifies findings before reporting, two-pass review +
adversarial recheck, posts one labeled comment per model. Advisory only.

- cmd/gadfly: reviewer binary (majordomo + Ollama Cloud), zero deps beyond stdlib + majordomo
- entrypoint.sh: container brains — trigger gating, PR clone, model loop (logic out of YAML)
- Dockerfile: multi-stage; build-time module token never reaches the final image
- .gitea/workflows/build-image.yml: tag v* → build & push image
- examples/: ~15-line consumer stub
- system prompt genericized + hardened to re-derive constants/formulas (semantic bugs)

Vibe-coded with Claude Code; see README disclosure. Advisory, never blocks merge.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

examples/adversarial-review.yml

@@ -0,0 +1,52 @@
+# Drop this in ANY Gitea repo at .gitea/workflows/adversarial-review.yml to turn
+# Gadfly on. The image holds all the logic; this stub just forwards the event
+# context. Advisory only — it never blocks a merge.
+#
+# Per-repo setup (no code changes needed):
+#   secret  OLLAMA_CLOUD_API_KEY   your Ollama Cloud key
+#   var     OLLAMA_REVIEW_MODELS   (optional) comma-separated model ids
+#   var     GADFLY_ALLOWED_USERS   (optional) who may "@gadfly review"; empty =
+#                                  any repo collaborator
+# GITEA_TOKEN is provided automatically; comments post as the gitea-actions user.
+
+name: Adversarial Review (Gadfly)
+
+on:
+  pull_request:
+    types: [opened, reopened, ready_for_review]
+  issue_comment:
+    types: [created]
+  workflow_dispatch:
+    inputs:
+      pr_number:
+        description: "PR number to review"
+        required: true
+
+permissions:
+  contents: read
+  issues: write
+  pull-requests: write
+
+concurrency:
+  group: gadfly-${{ github.event.issue.number || github.event.pull_request.number || github.event.inputs.pr_number }}
+  cancel-in-progress: true
+
+jobs:
+  review:
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    steps:
+      - uses: docker://gitea.stevedudenhoeffer.com/steve/gadfly:v1
+        env:
+          GITEA_API: ${{ github.server_url }}/api/v1/repos/${{ github.repository }}
+          GITEA_TOKEN: ${{ secrets.GITEA_TOKEN }}
+          OLLAMA_CLOUD_API_KEY: ${{ secrets.OLLAMA_CLOUD_API_KEY }}
+          OLLAMA_REVIEW_MODELS: ${{ vars.OLLAMA_REVIEW_MODELS }}
+          GADFLY_ALLOWED_USERS: ${{ vars.GADFLY_ALLOWED_USERS }}
+          EVENT_NAME: ${{ github.event_name }}
+          PR: ${{ github.event.pull_request.number || github.event.issue.number || github.event.inputs.pr_number }}
+          PR_BRANCH: ${{ github.head_ref }}
+          IS_DRAFT: ${{ github.event.pull_request.draft }}
+          COMMENT_BODY: ${{ github.event.comment.body }}
+          COMMENT_ID: ${{ github.event.comment.id }}
+          ACTOR: ${{ github.actor }}