ci: fix duplicate runs and combine fmt/clippy/test (#13)

## What
Fix CI workflow to eliminate duplicate job runs and reduce total number
of checks.

## Why
CI was showing 16 checks with duplicates (Check x2, Rustfmt x2, Clippy
x2, etc.) because both `push` and `pull_request` events were firing for
the same commits.

## How
- Remove `claude/**` from push triggers (PRs handle branch CI via
`pull_request` event)
- Add concurrency group to cancel in-progress runs when new commits are
pushed
- Combine `check`, `fmt`, `clippy`, `test` into single `ci` job

## Result
- Before: 7 jobs running twice = 14+ checks
- After: 4 jobs running once = 4 checks (ci, build, doc, examples)

## Risk
- Low
- CI behavior change only, no code changes

### Checklist
- [x] CI passes
- [x] No code changes, workflow only

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: chaliy

.github/workflows/ci.yml

@@ -2,9 +2,13 @@ name: CI
 
 on:
   push:
-    branches: [main, "claude/**"]
-  pull_request:
     branches: [main]
+  pull_request:
+
+# Cancel in-progress runs for same PR/branch
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
 
 permissions:
   contents: read
@@ -14,47 +18,20 @@ env:
   RUST_BACKTRACE: 1
 
 jobs:
-  check:
-    name: Check
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v4
-      - uses: dtolnay/rust-toolchain@stable
-      - uses: Swatinem/rust-cache@v2
-      - name: Check
-        run: cargo check --workspace --all-targets
-
-  fmt:
-    name: Rustfmt
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v4
-      - uses: dtolnay/rust-toolchain@stable
-        with:
-          components: rustfmt
-      - name: Check formatting
-        run: cargo fmt --all -- --check
-
-  clippy:
-    name: Clippy
+  ci:
+    name: Test
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@stable
         with:
-          components: clippy
+          components: rustfmt, clippy
       - uses: Swatinem/rust-cache@v2
+      - name: Format
+        run: cargo fmt --all -- --check
       - name: Clippy
         run: cargo clippy --workspace --all-targets -- -D warnings
-
-  test:
-    name: Test
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v4
-      - uses: dtolnay/rust-toolchain@stable
-      - uses: Swatinem/rust-cache@v2
-      - name: Run tests
+      - name: Test
         run: cargo test --workspace
 
   build: