Fix CI workflows: Add SentencePiece dependency

All workflows were failing with:
  CMake Error: Could not find SentencePiece.
  Install via: brew install sentencepiece

Changes:
- Added sentencepiece to all brew install commands across workflows
- Updated ci.yml (cpp-build and cpp-tests jobs)
- Updated release.yml (build-app job)
- Updated daemon-test.yml (all 4 jobs)
- Updated README.md to document SentencePiece requirement

SentencePiece is required by CMake build for tokenization support.
It's available via Homebrew on GitHub's macOS runners.

This fixes the build error preventing Metal kernel compilation,
C++ builds, and all subsequent tests from running.

Author: claude

.github/workflows/README.md

@@ -27,6 +27,7 @@ This directory contains GitHub Actions workflows for continuous integration, tes
 - macOS 14 (Sonoma) runner with Apple Silicon
 - Xcode with Metal compiler
 - MLX framework via Homebrew
+- SentencePiece via Homebrew (for tokenization)
 
 **Example:** Every push to a branch automatically:
 - Compiles Metal kernels
@@ -61,6 +62,7 @@ This directory contains GitHub Actions workflows for continuous integration, tes
 **Requirements:**
 - macOS 14 runner
 - Node.js for UI build
+- SentencePiece for tokenization
 - XcodeGen (optional, for project generation)
 
 **Usage:**
@@ -98,6 +100,7 @@ git push origin v1.0.0
 
 **Requirements:**
 - macOS 14 runner
+- MLX and SentencePiece via Homebrew
 - ApacheBench for stress testing
 
 **Example Tests:**
@@ -200,6 +203,7 @@ curl http://127.0.0.1:11434/health
 - Check CMake configuration in `CMakeLists.txt`
 - Verify dependencies: `brew list`
 - Check MLX installation: `python -c "import mlx"`
+- Ensure SentencePiece is installed: `brew list sentencepiece`
 
 **Daemon fails to start:**
 - Check for port conflicts: `lsof -i :11434`

.github/workflows/ci.yml

@@ -54,7 +54,7 @@ jobs:
 
       - name: Install dependencies
         run: |
-          brew install cmake ninja mlx
+          brew install cmake ninja mlx sentencepiece
 
       - name: Download Metal libraries
         uses: actions/download-artifact@v4
@@ -101,7 +101,7 @@ jobs:
 
       - name: Install dependencies
         run: |
-          brew install mlx
+          brew install mlx sentencepiece
 
       - name: Download Metal libraries
         uses: actions/download-artifact@v4

.github/workflows/daemon-test.yml

@@ -29,7 +29,7 @@ jobs:
 
       - name: Install dependencies
         run: |
-          brew install cmake ninja mlx
+          brew install cmake ninja mlx sentencepiece
 
       - name: Set up Conda
         uses: conda-incubator/setup-miniconda@v3
@@ -91,7 +91,7 @@ jobs:
 
       - name: Install dependencies
         run: |
-          brew install mlx
+          brew install mlx sentencepiece
 
       - name: Download daemon artifacts
         uses: actions/download-artifact@v4
@@ -143,7 +143,7 @@ jobs:
 
       - name: Install dependencies
         run: |
-          brew install mlx
+          brew install mlx sentencepiece
 
       - name: Download daemon artifacts
         uses: actions/download-artifact@v4
@@ -260,7 +260,7 @@ jobs:
 
       - name: Install dependencies
         run: |
-          brew install mlx apache-bench
+          brew install mlx sentencepiece apache-bench
 
       - name: Download daemon artifacts
         uses: actions/download-artifact@v4

.github/workflows/release.yml

@@ -40,7 +40,7 @@ jobs:
 
       - name: Install dependencies
         run: |
-          brew install cmake ninja mlx node
+          brew install cmake ninja mlx sentencepiece node
 
       - name: Set up Conda
         uses: conda-incubator/setup-miniconda@v3