ci: fix cliff.toml tag casing, add PR title validation workflow

- Fix trim_start_matches to use uppercase V matching tag convention
- Add comment documenting tag_pattern scope (V0.1.7+ only)
- Simplify git-cliff install instructions (releases page + brew/winget)
- Add PR title validation workflow using semantic-pull-request action
- Add cliff.toml to .Rbuildignore

Author: shamykyzer

.Rbuildignore

@@ -24,5 +24,6 @@
 ^\.vscode$
 ^.*\.swp$
 ^\.Rdata$
+^cliff\.toml$
 ^doc$
 ^Meta$

.github/workflows/pr-title.yaml

@@ -0,0 +1,30 @@
+name: PR Title
+
+on:
+  pull_request:
+    types: [opened, edited, synchronize]
+    branches: [main]
+
+permissions:
+  pull-requests: read
+
+jobs:
+  validate:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: amannn/action-semantic-pull-request@v5
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          types: |
+            feat
+            fix
+            docs
+            style
+            refactor
+            perf
+            test
+            build
+            ci
+            chore
+            revert

CONTRIBUTING.md

@@ -98,15 +98,14 @@ revert — reverts an earlier commit
 
 ### Install git-cliff
 
-```shell
-# pip
-pip install git-cliff
-
-# uv
-uv tool install git-cliff
+Download a prebuilt binary from the [releases page](https://github.com/orhun/git-cliff/releases) or install via a package manager:
 
+```shell
 # homebrew (macOS / Linux)
 brew install git-cliff
+
+# winget (Windows)
+winget install git-cliff
 ```
 
 ### Generate the changelog entry

cliff.toml

@@ -2,7 +2,7 @@
 header = ""
 body = """
 {% if version %}\
-# acro {{ version | trim_start_matches(pat="v") }}
+# acro {{ version | trim_start_matches(pat="V") }}
 
 {% else %}\
 # Unreleased
@@ -18,6 +18,8 @@ footer = ""
 [git]
 conventional_commits = true
 filter_unconventional = true
+# Only matches uppercase V tags (V0.1.7+); older lowercase tags
+# (v0.1.1–v0.1.6) are excluded — their NEWS.md entries were hand-written.
 tag_pattern = "V[0-9]+\\.[0-9]+\\.[0-9]+"
 
 commit_preprocessors = [