settings: Migration for fixing duplicated agent keys (#30237)

As a byproduct, this fixes bug where it's impossible to change Agent
profile

Closes #30000 

Release Notes:

- N/A

crates/migrator/src/migrations/m_2025_05_08/settings.rs

@@ -0,0 +1,26 @@
+use std::ops::Range;
+use tree_sitter::{Query, QueryMatch};
+
+use crate::{MigrationPatterns, patterns::SETTINGS_DUPLICATED_AGENT_PATTERN};
+
+pub const SETTINGS_PATTERNS: MigrationPatterns =
+    &[(SETTINGS_DUPLICATED_AGENT_PATTERN, comment_duplicated_agent)];
+
+fn comment_duplicated_agent(
+    contents: &str,
+    mat: &QueryMatch,
+    query: &Query,
+) -> Option<(Range<usize>, String)> {
+    let pair_ix = query.capture_index_for_name("pair1")?;
+    let mut range = mat.nodes_for_capture_index(pair_ix).next()?.byte_range();
+
+    // Include the comma into the commented region
+    let rtext = &contents[range.end..];
+    if let Some(comma_index) = rtext.find(',') {
+        range.end += comma_index + 1;
+    }
+
+    let value = contents[range.clone()].to_string();
+    let commented_value = format!("/* Duplicated key auto-commented: {value} */");
+    Some((range, commented_value))
+}