fix: configure git author in opencode workflow

Add a Configure git author step after checkout to set
github-actions[bot] as the git identity, fixing the
'Author identity unknown' error when OpenCode tries to commit.

Update .opencode/README.md to document the git author setup
and explain that write tasks need this identity.

Author: mahyarmlk

.github/workflows/opencode.yml

@@ -24,6 +24,11 @@ jobs:
           fetch-depth: 1
           persist-credentials: false
 
+      - name: Configure git author
+        run: |
+          git config --global user.name "github-actions[bot]"
+          git config --global user.email "41898282+github-actions[bot]@users.noreply.github.com"
+
       - name: Run OpenCode
         uses: anomalyco/opencode/github@latest
         env:

.opencode/README.md

@@ -104,6 +104,22 @@ env:
 `GITHUB_TOKEN` is passed so the action can authenticate as the workflow runner
 when `use_github_token: true`.
 
+### Git author identity
+
+The workflow configures `github-actions[bot]` as the git author for OpenCode
+commits via a `Configure git author` step after checkout:
+
+```yaml
+- name: Configure git author
+  run: |
+    git config --global user.name "github-actions[bot]"
+    git config --global user.email "41898282+github-actions[bot]@users.noreply.github.com"
+```
+
+`/oc` read-only tasks (e.g. review, inspect) work without commits, but write
+tasks (implement, edit, create PRs) need this git identity to be set, otherwise
+OpenCode cannot commit changes.
+
 ### Merge behavior
 
 The workflow does not merge automatically. It opens or updates PRs and reports