feat: opencode review engine + .opencode factory

Replace the single Python model-call reviewer with an opencode agent
factory. A primary 'pragent' agent reads a brief (title/body/diff/config/
prior reviews), inspects the checked-out repo, runs the repo's own linters
via bash, loads review-methodology + findings-schema skills, and emits a
{summary, findings} JSON with per-finding severity/path/line/problem/fix/
suggestion/reference. Dormant security/tests/perf subagent lenses fan out
only on large/risky diffs (lean by default).

pilot/opencode_review.py: fetches the repo archive at the head sha into a
temp workdir, writes .pragent/brief.md, drops the factory, runs
'opencode run --pure --agent pragent --dir <workdir>' headlessly. Isolates
HOME (shared, warmed), strips ANTHROPIC_* env (leaked host vars caused
ProviderModelNotFoundError), stdin=DEVNULL (opencode blocks on stdin),
maps the bare OLLAMA_MODEL to the provider-prefixed ref. No Gitea I/O —
ai_review.review_pr parses + anchors + posts (reuses all v2 logic/tests).

PRAGENT_ENGINE=opencode (default) selects it; =ollama keeps the legacy
direct-call path. Verified end-to-end: posts a real review with a summary
section, inline [CRITICAL]/[HIGH] comments + apply-able suggestions +
reference links, and the sha dedupe marker. 49 tests pass.

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

opencode.json

@@ -0,0 +1,40 @@
+{
+  "$schema": "https://opencode.ai/config.json",
+  "default_agent": "pragent",
+  "model": "headroom/glm-5.2:cloud",
+  "small_model": "headroom/glm-5.2:cloud",
+  "provider": {
+    "headroom": {
+      "npm": "@ai-sdk/anthropic",
+      "name": "Headroom GLM",
+      "options": {
+        "baseURL": "http://100.74.17.70:8789/v1",
+        "apiKey": "ollama"
+      },
+      "models": {
+        "glm-5.2:cloud": {
+          "name": "GLM 5.2 Cloud",
+          "limit": { "context": 200000, "output": 16000 }
+        }
+      }
+    }
+  },
+  "lsp": {},
+  "permission": {
+    "*": "allow",
+    "edit": "deny",
+    "write": "deny",
+    "apply_patch": "deny",
+    "bash": {
+      "*": "allow",
+      "rm -rf *": "deny",
+      "rm -fr *": "deny",
+      "git push *": "deny",
+      "git commit *": "deny",
+      "git reset --hard*": "deny",
+      "sudo *": "deny"
+    },
+    "external_directory": "allow",
+    "doom_loop": "deny"
+  }
+}