feat: update skill

Author: indietyp

.claude/skills/testing-hashql/SKILL.md

@@ -180,6 +180,12 @@ For testing MIR transformation and analysis passes directly with programmaticall
 - Edge cases requiring specific MIR structures hard to produce from source
 - Benchmarking pass performance
 
+**Key features:**
+
+- Transform passes return `Changed` enum (`Yes`, `No`, `Unknown`) to indicate modifications
+- Test harness captures and includes `Changed` value in snapshots for verification
+- Snapshot format: before MIR → `Changed: Yes/No/Unknown` separator → after MIR
+
 **Quick Example:**
 
 ```rust
@@ -201,10 +207,10 @@ builder
 let body = builder.finish(0, TypeBuilder::synthetic(&env).integer());
 ```
 
-📖 **Full Guide:** [resources/mir-builder-guide.md](resources/mir-builder-guide.md)
+📖 **Full Guide:** [references/mir-builder-guide.md](references/mir-builder-guide.md)
 
 ## References
 
-- [compiletest Guide](resources/compiletest-guide.md) - Detailed UI test documentation
-- [Testing Strategies](resources/testing-strategies.md) - Choosing the right approach
-- [MIR Builder Guide](resources/mir-builder-guide.md) - Programmatic MIR construction for tests
+- [compiletest Guide](references/compiletest-guide.md) - Detailed UI test documentation
+- [Testing Strategies](references/testing-strategies.md) - Choosing the right approach
+- [MIR Builder Guide](references/mir-builder-guide.md) - Programmatic MIR construction for tests

.claude/skills/testing-hashql/references/mir-builder-guide.md

@@ -228,10 +228,11 @@ builder.build_block(bb_merge).ret(x);  // x receives value from param
 
 ## Test Harness Pattern
 
-Standard pattern used across transform pass tests:
+Standard pattern used across transform pass tests. The harness captures and displays
+the `Changed` return value to verify pass behavior:
 
 ```rust
-use std::path::PathBuf;
+use std::{io::Write as _, path::PathBuf};
 use bstr::ByteVec as _;
 use hashql_core::{
     pretty::Formatter,
@@ -274,12 +275,16 @@ fn assert_pass<'heap>(
         .format(DefIdSlice::from_raw(&bodies), &[])
         .expect("should be able to write bodies");
 
-    text_format
-        .writer
-        .extend(b"\n\n------------------------------------\n\n");
-
-    // Run the pass
-    YourPass::new().run(context, &mut bodies[0]);
+    // Run the pass and capture change status
+    let changed = YourPass::new().run(context, &mut bodies[0]);
+    
+    // Include Changed value in snapshot for verification
+    write!(
+        text_format.writer,
+        "\n\n{:=^50}\n\n",
+        format!(" Changed: {changed:?} ")
+    )
+    .expect("infallible");
 
     // Format after
     text_format