fix: address PR review — lcov/valgrind in Dockerfile, correct cmake-expert.md, expand AGENTS.md

AGENTS.md

@@ -9,16 +9,38 @@ FastSync is a high-performance file synchronization system written in C11. It su
 The image is built from the repo-root `Dockerfile` and is the same image CI uses: `gitea.tap-tap.win/taptap/fastsync-ci:v7`. It contains the full toolchain: gcc/g++, CMake, libzstd-dev, libssl-dev, make, git, cppcheck, clang-format, python3 + pytest, openssh-client, and Node.js.
 
 ```bash
-# Build the image from the repo-root Dockerfile
+# Use the prebuilt CI image directly (faster, guaranteed CI parity)
+docker pull gitea.tap-tap.win/taptap/fastsync-ci:v7
+docker tag gitea.tap-tap.win/taptap/fastsync-ci:v7 fastsync-ci:local
+
+# Or build the image from the repo-root Dockerfile
 docker build -t fastsync-ci:local .
 
-# Provision dependencies and build inside the container (repo mounted at /workspace)
+# Build, run unit tests, and run integration tests inside the container
 docker run --rm -v "$PWD:/workspace" -w /workspace fastsync-ci:local \
-  sh -c 'cmake -B build -S . && cmake --build build -j$(nproc)'
+  sh -c 'cmake -B build -S . && cmake --build build -j$(nproc) && ./build/tests && python3 -m pytest tests/'
+
+# Avoid root-owned build/ artifacts by matching your host UID/GID
+docker run --rm --user "$(id -u):$(id -g)" -v "$PWD:/workspace" \
+  -w /workspace fastsync-ci:local \
+  sh -c 'cmake -B build -S . && cmake --build build -j$(nproc) && ./build/tests && python3 -m pytest tests/'
 ```
 
+> **Note:** The first `cmake configure` (`cmake -B build -S .`) fetches xxHash from GitHub via `FetchContent` — network access is required. Subsequent reconfigures reuse the cached source.
+
 If a dependency is missing from the image, add it to the `Dockerfile` (and rebuild) rather than installing it on the host.
 
+## CI Conventions
+
+When configuring for CI parity, use:
+```bash
+cmake -B build -S . -DSTRICT_WARNINGS=ON        # -Wextra -Wpedantic -Werror
+cmake -B build -S . -DSANITIZER=address           # AddressSanitizer (ASan)
+cmake -B build -S . -DSANITIZER=thread            # ThreadSanitizer (TSan)
+```
+
+The CI workflow (`.gitea/workflows/ci.yaml`) runs lint (clang-format, cppcheck), build + test (unit + integration), and sanitizer jobs sequentially.
+
 ## Build
 
 ```bash