{Misc.} Add Copilot instructions to prevent manual HISTORY.rst edits

.github/instructions/history-rst.instructions.md

@@ -0,0 +1,28 @@
+---
+applyTo: "{src/azure-cli/HISTORY.rst,src/azure-cli-core/HISTORY.rst}"
+description: "Do not manually edit HISTORY.rst files; release history is generated automatically."
+---
+
+When reviewing or editing changes in this repository:
+
+- Do **not** manually add, modify, or delete entries in any `HISTORY.rst` file
+  (for example `src/azure-cli/HISTORY.rst` or `src/azure-cli-core/HISTORY.rst`).
+  Release history notes are generated automatically from PR titles and descriptions
+  by the release pipeline (`scripts/release/generate_history_notes.py`).
+- During PR review, if a pull request contains manual changes to a `HISTORY.rst`
+  file, request that the author revert those changes while preserving the
+  functional (non-`HISTORY.rst`) changes. Reviewers consistently ask contributors
+  to "revert the changes to the HISTORY.rst, as the history notes would be
+  generated automatically."
+- To control what appears in the release history, use the PR title and the
+  `History Notes` section of the PR description instead of editing `HISTORY.rst`:
+  - A `[Component Name]` title prefix marks a customer-facing change that will be
+    added to `HISTORY.rst`; a `{Component Name}` prefix marks a change that will
+    **not** be included.
+  - See `doc/authoring_command_modules/README.md` ("Format PR Title" and
+    "Format PR Description") for the required format.
+- The only exception is a **Hotfix** PR targeting the `release` branch: per
+  `doc/authoring_command_modules/README.md`, customer-facing hotfixes must
+  manually add their history notes because the auto-generated notes ignore
+  PRs marked `Hotfix`. Outside this hotfix flow, manual `HISTORY.rst` edits
+  should be reverted.