docs: adopt two-step rename+translate commit structure in xtend-to-java skill

.agents/skills/xtend-to-java/workflow/formatting-and-commit.md

@@ -65,22 +65,44 @@ Select all migrated files in Package Explorer → Source → Format. Then amend
 
 The Eclipse formatter re-indents text block content AND closing `"""` together, preserving indent stripping semantics. Formatted text blocks produce the same string values as unformatted ones — the formatter is safe for text blocks.
 
-## Commit structure
-
-**One single commit** containing everything:
-- Migrated `.java` files
-- Deleted `.xtend` originals
-- Deleted `xtend-gen/` directory (if module fully off Xtend)
-- All infrastructure changes (MANIFEST.MF, build.properties, .classpath, .project)
-
-Do not split into multiple commits.
+## Commit structure — two-step rename → translate
+
+Structure every migration slice as **two commits plus an optional infrastructure commit**:
+
+1. **Rename commit** — a pure `git mv` of every `.xtend` in the slice to `.java`, content
+   **unchanged**. Because the rename edge has 100% content similarity, Git's rename detection
+   always traverses it: `git log --follow` and `git blame` permanently connect the `.java`
+   history to its `.xtend` past. (Git stores no rename metadata — a combined delete+add commit
+   only keeps history if the finished Java stays >50% similar to the Xtend source, which heavy
+   rewrites don't.)
+2. **Translate commit** — rewrite the renamed files **in place** to the final Java. Reviewers
+   get a side-by-side Xtend-vs-Java diff per file on the PR's Commits tab (the paths are
+   unchanged, so the pairing is guaranteed regardless of similarity). Put the per-file
+   faithfulness notes (null-semantics decisions, documented deviations) in this commit's body.
+3. **Infrastructure commit** (only when the module is now fully off Xtend) — the
+   [`infrastructure-cleanup.md`](./infrastructure-cleanup.md) changes: build.properties,
+   .classpath, .project, `xtend-gen/` deletion, MANIFEST check.
+
+Known trade-offs (accepted):
+- The rename commit **intentionally does not compile** (Xtend syntax in `.java` files). PR CI
+  only builds the head, so CI stays green; after a rebase-merge the intermediate commit costs
+  one `git bisect skip` on master.
+- The aggregate **Files-changed tab is unaffected** by the commit structure: it diffs
+  base…head and pairs old/new only when end-state similarity crosses Git's threshold.
+  Near-transliterations pair either way; heavy rewrites pair under neither. Point reviewers to
+  the Commits tab for the guaranteed in-place diff.
+
+Do not split the translate step per file — every intermediate commit before the last file
+would be broken anyway, so per-file translate commits only multiply the broken range.
 
 ## Commit message format
 
 ```
-refactor: migrate Xtend to Java - <plugin name>
+refactor: migrate Xtend to Java - <plugin name> (1/2: rename sources)
+refactor: migrate Xtend to Java - <plugin name> (2/2: translate to Java 21)
+refactor: drop Xtend build infrastructure from <plugin name>   # when applicable
 ```
 
-Example: `refactor: migrate Xtend to Java - com.avaloq.tools.ddk.check.core.test`
+The rename commit body must state that it is a pure `git mv` and intentionally non-compiling.
 
-PR title: same as commit message.
+PR title: `refactor: migrate Xtend to Java - <plugin name>`.

.agents/skills/xtend-to-java/workflow/multi-file-batch.md

@@ -42,12 +42,14 @@ A red gate means you do not start the next batch. Diagnose first.
 
 ### Commit structure
 
-**One single commit per module** containing everything: migrated Java files, deleted `.xtend`
-originals, deleted `xtend-gen/` directory (if module is fully off Xtend), and all infrastructure changes.
+**Two-step rename → translate per module** (see [`formatting-and-commit.md`](./formatting-and-commit.md)):
+a pure `git mv` rename commit for all `.xtend` in the slice, an in-place translate commit, and —
+when the module is fully off Xtend — an infrastructure-cleanup commit.
 
 Commit message format:
 ```
-refactor: migrate Xtend to Java - <plugin name>
+refactor: migrate Xtend to Java - <plugin name> (1/2: rename sources)
+refactor: migrate Xtend to Java - <plugin name> (2/2: translate to Java 21)
 ```
 Example: `refactor: migrate Xtend to Java - com.avaloq.tools.ddk.check.core.test`
 

.agents/skills/xtend-to-java/workflow/validation-checklist.md

@@ -83,7 +83,7 @@ Run through this list before declaring a conversion done. Every item is a hard g
 | # | Rule | Requirement |
 |---|------|-------------|
 | 21 | Copyright headers | File starts with the exact Avaloq `/**…**/` banner header (see [`formatting-and-commit.md`](./formatting-and-commit.md)). This **replaces** any header the source carried — a `/* generated by Xtext x.y */` stub marker or a `/** … */` Javadoc-style copyright block. Normalising to the banner is **not** "inventing" (rule 1 does not apply to the copyright header). Match a sibling `.java` in the module. |
-| 22 | Commit format | `refactor: migrate Xtend to Java - <plugin name>`. Single commit. |
+| 22 | Commit format | Two-step: `(1/2: rename sources)` pure `git mv` commit + `(2/2: translate to Java 21)` in-place rewrite commit (+ infra commit when module fully off Xtend). See [`formatting-and-commit.md`](./formatting-and-commit.md). |
 | 28 | Infrastructure cleanup | Remove Xtend from MANIFEST.MF, build.properties, .classpath, .project; delete `xtend-gen/` directory (when module fully off Xtend). |
 
 ### Migration-campaign gates (learned)