doc: add an AI contribution policy

Document project expectations for AI-assisted contributions so contributors
understand when AI use is acceptable and when it creates review or moderation
burden.

Link to the document directly from the new PR and issues helptext.

.github/ISSUE_TEMPLATE/bug.yml

@@ -10,6 +10,7 @@ body:
         * General bitcoin questions and/or support requests should use Bitcoin StackExchange at https://bitcoin.stackexchange.com.
         * For reporting security issues, please read instructions at https://bitcoincore.org/en/contact/.
         * If the node is "stuck" during sync or giving "block checksum mismatch" errors, please ensure your hardware is stable by running `memtest` and observe CPU temperature with a load-test tool such as `linpack` before creating an issue.
+        * If you use AI tools when opening this issue, please read the [AI policy](https://github.com/bitcoin/bitcoin/blob/master/doc/AI_POLICY.md).
 
         ----
   - type: checkboxes

.github/ISSUE_TEMPLATE/feature_request.yml

@@ -2,6 +2,11 @@ name: Feature Request
 description: Suggest an idea for this project.
 labels: [Feature]
 body:
+  - type: markdown
+    attributes:
+      value: |
+        If you use AI tools when opening this issue, please read the [AI policy](https://github.com/bitcoin/bitcoin/blob/master/doc/AI_POLICY.md).
+
   - type: textarea
     id: feature
     attributes:

.github/ISSUE_TEMPLATE/gui_issue.yml

@@ -2,6 +2,11 @@ name: Issue or feature request related to the GUI
 description: Any report, issue or feature request related to the GUI
 labels: [GUI]
 body:
+- type: markdown
+  attributes:
+    value: |
+      If you use AI tools when opening this issue, please read the [AI policy](https://github.com/bitcoin/bitcoin/blob/master/doc/AI_POLICY.md).
+
 - type: checkboxes
   id: acknowledgement
   attributes:

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,12 +1,13 @@
 <!--
 *** Please remove the following help text before submitting: ***
 
-Pull requests without a rationale and clear improvement may be closed
-immediately.
+Pull requests may be closed immediately if they:
+- do not have a rationale and clear improvement
+- do not adhere to doc/AI_POLICY.md
 
 GUI-related pull requests should be opened against
-https://github.com/bitcoin-core/gui
-first. See CONTRIBUTING.md
+https://github.com/bitcoin-core/gui first.
+See CONTRIBUTING.md
 -->
 
 <!--