chore: remove generated ANTLR parser from git; add CI grammar step (#514)

The generated mdl/grammar/parser/ files (~120k lines of mdl_parser.go)
are deterministically derived from the .g4 source. Tracking them causes
unresolvable merge conflicts whenever two branches run make grammar.

Changes:
- .gitignore: ignore mdl/grammar/parser/ directory
- git rm --cached: untrack 8 generated files (4 .go, 2 .interp, 2 .tokens)
- CI workflows: add ANTLR4 install + make grammar before make build/release
  in push-test.yml, release.yml, and nightly.yml (both jobs)
- JAR cached at ~/.m2/repository/org/antlr/antlr4 with key antlr4-4.13.2
  to avoid re-downloading on every run

The devcontainer Dockerfile already installs antlr4-tools; no change needed
there. Run 'make grammar' after editing any .g4 file.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: ako

.github/workflows/nightly.yml

@@ -24,6 +24,15 @@ jobs:
         with:
           go-version: '1.26'
 
+      - name: Cache ANTLR4 JAR
+        uses: actions/cache@v4
+        with:
+          path: ~/.m2/repository/org/antlr/antlr4
+          key: antlr4-4.13.2
+      - name: Install ANTLR4
+        run: pip install 'antlr4-tools==0.2.2'
+      - name: Generate parser
+        run: make grammar
       - name: Build
         run: make build
 
@@ -51,6 +60,16 @@ jobs:
 
       - uses: oven-sh/setup-bun@v2
 
+      - name: Cache ANTLR4 JAR
+        uses: actions/cache@v4
+        with:
+          path: ~/.m2/repository/org/antlr/antlr4
+          key: antlr4-4.13.2
+      - name: Install ANTLR4
+        run: pip install 'antlr4-tools==0.2.2'
+      - name: Generate parser
+        run: make grammar
+
       - name: Check for new commits since last nightly
         id: check
         run: |

.github/workflows/push-test.yml

@@ -13,6 +13,15 @@ jobs:
       - uses: actions/setup-go@v6
         with:
           go-version: '1.26'
+      - name: Cache ANTLR4 JAR
+        uses: actions/cache@v4
+        with:
+          path: ~/.m2/repository/org/antlr/antlr4
+          key: antlr4-4.13.2
+      - name: Install ANTLR4
+        run: pip install 'antlr4-tools==0.2.2'
+      - name: Generate parser
+        run: make grammar
       - name: Build
         run: make build
       - name: Test

.github/workflows/release.yml

@@ -19,6 +19,15 @@ jobs:
         with:
           go-version: '1.26'
       - uses: oven-sh/setup-bun@v2
+      - name: Cache ANTLR4 JAR
+        uses: actions/cache@v4
+        with:
+          path: ~/.m2/repository/org/antlr/antlr4
+          key: antlr4-4.13.2
+      - name: Install ANTLR4
+        run: pip install 'antlr4-tools==0.2.2'
+      - name: Generate parser
+        run: make grammar
       - name: Build release binaries
         run: make release
       - name: Create GitHub Release

.gitignore

@@ -39,6 +39,8 @@ mx-test-projects/*/
 tmp/
 
 # Generated files
+# ANTLR4 parser (regenerate with: make grammar)
+mdl/grammar/parser/
 *.pdf
 *.tar
 *.tgz