Add branching-strategy skill with next and create actions

Version-aware branch naming (X.Y.Z.Q/{TASK_CODE}-{FEATURE}-{SEQ}),
branch creation from origin/test with origin/main fallback, and the
PR-into-test merge rule. Ships a TypeScript CLI (next, create) plus
shell modules (loggers, base, cli) run via Taskfile.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

scripts/.gitignore

@@ -0,0 +1,16 @@
+# Node / pnpm
+node_modules/
+dist/
+.pnpm-store/
+
+# Build artefacts
+*.js.map
+*.d.ts.map
+
+# Environment
+.env
+.env.local
+.env.*.local
+
+# OS
+.DS_Store