[ai] add .aiconfig (#8894)

Verified in vscode.

<img width="1420" height="1808" alt="image"
src="https://github.com/user-attachments/assets/6fea2d51-2ef1-478e-b977-a3861cb45352"
/>




Fixes: #8893



---

Review the contribution guidelines below:

- [x] I’ve reviewed the contributor guide and applied the relevant
portions to this PR.
- [x] I've included the required information in the description above.
- [x] My up-to-date information is in the `AUTHORS` file.
- [x] I've updated `CHANGELOG.md` if appropriate.

<details>
  <summary>Contribution guidelines:</summary><br>

- See
  our [contributor guide](../CONTRIBUTING.md) and
the [Flutter organization contributor
guide]([https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md)
  for general expectations for PRs.
- Larger or significant changes should be discussed in an issue before
creating a PR.
- Dart contributions to our repos should follow the [Dart style
guide](https://dart.dev/guides/language/effective-dart) and use
  `dart format`.
- Java and Kotlin contributions should strive to follow Java and Kotlin
best
practices
([discussion](#8098)).

</details>

Author: pq

.aiconfig

@@ -0,0 +1,21 @@
+# Gemini Code Assist Configuration
+version: 1.0
+project:
+  context:
+    instruction_files:
+      - .gemini/styleguide.md
+
+  generation_rules:
+    - "Strictly adhere to the IntelliJ Platform Threading Model: No I/O on the EDT."
+    - "All generated AnAction classes must be stateless."
+    - "Apply [MUST-FIX], [CONCERN], and [NIT] severity logic to any code suggestions that violate plugin SDK best practices or style guidelines."
+    - "Use io.flutter.logging.PluginLogger for all logging; avoid System.out."
+    - "Always include the standard Chromium Authors copyright header in new files."
+    - "Adhere to the Zero-Formatting Policy: Do not comment on indentation, spacing, or brace placement."
+    # Ensure local agents read styleguide files automatically.
+    - "At the start of the session, read and adhere to the guidelines in all files listed in project.context.instruction_files."
+
+  languages:
+    - java
+    - kotlin
+    - dart