chore: optimize CI — path filters, concurrency, skip release builds on PRs

.github/workflows/ci.yml

@@ -2,9 +2,20 @@ name: CI
 
 on:
   push:
-    branches: [master]
+    branches: [master, main]
   pull_request:
-    branches: [master]
+    branches: [master, main]
+    paths:
+      - '**/*.rs'
+      - '**/Cargo.toml'
+      - '**/Cargo.lock'
+      - '.github/workflows/**'
+      - 'Makefile'
+  workflow_dispatch:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
 
 env:
   CARGO_TERM_COLOR: always
@@ -100,9 +111,10 @@ jobs:
           echo "- Setpoints: **${SETPOINTS}**" >> "$GITHUB_STEP_SUMMARY"
           echo "- Governance files: ✅" >> "$GITHUB_STEP_SUMMARY"
 
-  # Gate 5: Build verification
+  # Gate 5: Build verification (skip on PRs — release.yml handles tagged builds)
   build:
     name: Build (${{ matrix.target }})
+    if: github.event_name != 'pull_request'
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
@@ -131,6 +143,7 @@ jobs:
 
   docker:
     name: Docker Build
+    if: github.event_name != 'pull_request'
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4

.github/workflows/release.yml

@@ -4,6 +4,10 @@ on:
   push:
     tags: ["v*"]
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 permissions:
   contents: write