chore(dependabot): batch only minor and patch; a major opens its own PR

.github/dependabot.yml

@@ -14,6 +14,15 @@
 # allowlist policy, asserted by test/unit/test_install_pins.jl). Dependabot
 # advances those pins to the current SHA of the tracked version, so the
 # pinning policy itself survives updates.
+#
+# The #124 rule: minor and patch updates are batched, because they are
+# interchangeable in kind; a MAJOR (React 18->19, vite 6->8, TypeScript
+# 5->7 -- which #124 landed as one grouped PR, with the build already red
+# until #140 repaired it) is a migration, not an update. Every group below
+# therefore names its update-types as minor and patch ONLY: an update that
+# matches no group opens its own PR, carrying its own review and its own CI
+# run. test/unit/test_install_pins.jl asserts this shape, so a new group
+# cannot silently go back to batching majors.
 version: 2
 updates:
   # The frontend is Bun-managed: package.json plus bun.lock, no npm/yarn/pnpm
@@ -25,8 +34,10 @@ updates:
     commit-message:
       prefix: "chore(deps)"
     groups:
-      frontend:
+      # Minor and patch in one weekly PR; majors arrive one PR each.
+      frontend-minor-and-patch:
         patterns: ["*"]
+        update-types: ["minor", "patch"]
 
   - package-ecosystem: "github-actions"
     directory: "/"
@@ -35,5 +46,8 @@ updates:
     commit-message:
       prefix: "chore(deps)"
     groups:
-      actions:
+      # Same rule as the frontend: a new major of an action (checkout
+      # v4.4.0 -> v7.0.1 came through #123) gets a PR of its own.
+      actions-minor-and-patch:
         patterns: ["*"]
+        update-types: ["minor", "patch"]

test/unit/test_install_pins.jl

@@ -346,3 +346,33 @@ end
     end
     @test isempty(extras)
 end
+
+@testset "dependabot never batches a major" begin
+    # #124 grouped every frontend update, and with nothing requiring the
+    # checks it merged five framework majors (React 18->19, vite 6->8,
+    # TypeScript 5->7, react-router-dom 6->7, plotly 2->4) in one PR, with
+    # tsc already red until #140 repaired it. A major is a migration, not an
+    # update, so it must open its own PR: a Dependabot group only claims an
+    # update when its patterns match AND its update-types admit it -- a
+    # dependency matching no group gets its own PR. Every group must
+    # therefore NAME its update-types, and never "major". The frontend must
+    # also stay on the "bun" ecosystem: the 2026-09 security-update runs
+    # proved this account's npm_and_yarn updater refuses a Bun-managed
+    # project (see the header of .github/dependabot.yml).
+    dependabot = YAML.load_file(joinpath(REPO_ROOT, ".github", "dependabot.yml"))
+    @test dependabot["version"] == 2
+    ecosystems = Dict{String,Any}()
+    for u in dependabot["updates"]
+        @test !haskey(ecosystems, u["package-ecosystem"])
+        ecosystems[u["package-ecosystem"]] = u
+    end
+    @test sort(collect(keys(ecosystems))) == ["bun", "github-actions"]
+    @test ecosystems["bun"]["directory"] == "/frontend"
+    for u in dependabot["updates"]
+        for (_, group) in get(u, "groups", Dict{String,Any}())
+            update_types = get(group, "update-types", nothing)
+            @test update_types !== nothing
+            @test !("major" in update_types)
+        end
+    end
+end