[release/10.0] Port servicing-pr skill from main (#37990)

Co-authored-by: AndriySvyryd <6539701+AndriySvyryd@users.noreply.github.com>

Author: Copilot

.agents/skills/servicing-pr/SKILL.md

@@ -0,0 +1,65 @@
+---
+name: servicing-pr
+description: 'Create EF Core PRs targeting servicing release branches (release/*). Use when working on a PR that targets a release branch, backporting a fix from main, or when the user mentions servicing, patch, or release branch.'
+---
+
+# Servicing PRs
+
+PRs targeting `release/*` branches require a specific description format and should include a quirk (AppContext switch) when applicable.
+
+## Backport Target Branch
+
+- If a version is specified, target `release/XX.0` (e.g., `backport to 10` → `release/10.0`)
+- Otherwise, find the latest `release/XX.0` branch (ignore preview branches like `release/11.0-preview2`)
+- Verify the branch exists before creating the PR
+
+## PR Title
+
+`[release/XX.0] <original PR title>`
+
+## PR Description Template
+
+```
+Fixes #{issue_number}
+Backports #{source_pr_number_if_applicable}
+
+**Description**
+Provide information on the bug, why it occurs and how it was introduced. Put it in terms that developers can understand without knowledge of EF Core internals.
+
+**Customer impact**
+How the bug affects users without internal technical detail. Include a short (3-4 lines) code sample if possible. If data corruption occurs, state that explicitly. If a feasible workaround exists, briefly describe it and how discoverable it is, otherwise mention that there's no workaround.
+
+**How found**
+How the bug was discovered based on the information in the issue description. If user-reported, mention "User reported on <version>". If multiple users are affected, note that. Count the number of upvotes and comment authors to estimate impact.
+
+**Regression**
+Whether this is a regression from an earlier EF version. Add a link to the PR that introduced the regression if known. If it only affects a feature introduced in the same major version, it is not a regression.
+
+**Testing**
+State the number of new or modified tests, don't go into details. If test coverage is unfeasible, briefly explain the alternative validation approach that was used.
+
+**Risk**
+Brief risk assessment ranked from "extremely low" to "high". Note amount of code changed. If the fix is a one-liner, mention that. If a quirk was added, mention "Quirk added".
+```
+
+## Quirk (AppContext Switch)
+
+A quirk lets users opt out of the fix at runtime, reducing patch risk. Add for all cases where it makes sense. Skip when the fix is 100% obvious/risk-free, or when the quirk couldn't be used, like in tools or analyzers.
+
+### Adding a Quirk
+
+Add in the class(es) containing code changes:
+
+```csharp
+private static readonly bool UseOldBehavior37585 =
+    AppContext.TryGetSwitch("Microsoft.EntityFrameworkCore.Issue37585", out var enabled) && enabled;
+```
+
+- Change `37585` to the relevant issue number
+- Wrap changes with a condition on `!UseOldBehavior37585` so activating the switch bypasses the fix, prefer to minimize the number of times the switch is checked
+- If the PR closes multiple issues, pick the most appropriate one for the switch name
+
+## Validation
+
+- PR description follows the template completely (all sections filled)
+- Quirk added where appropriate with issue number matching the PR description