Refactor cockpit to use DockerTmuxController pattern

Based on claude-code-tools TmuxCLIController, this refactor:

- Added DockerTmuxController class for robust tmux session management
- Implements send_keys() with configurable delay_enter
- Implements capture_pane() for output retrieval
- Implements wait_for_prompt() for pattern-based completion detection
- Implements wait_for_idle() for content-hash-based idle detection
- Implements wait_for_shell_prompt() for shell prompt detection

Also includes workflow improvements:
- Pre-task git snapshot before agent execution
- Post-task commit protocol in agent guidelines

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docker/Dockerfile

@@ -0,0 +1,41 @@
+# Luzia Sandbox - Lightweight agent execution environment
+# Agents execute inside this container as project users
+
+FROM alpine:3.19
+
+# Install common tools agents need
+RUN apk add --no-cache \
+    bash \
+    git \
+    curl \
+    wget \
+    jq \
+    grep \
+    sed \
+    gawk \
+    findutils \
+    coreutils \
+    diffutils \
+    patch \
+    openssh-client \
+    nodejs \
+    npm \
+    python3 \
+    py3-pip \
+    make \
+    gcc \
+    g++ \
+    musl-dev
+
+# Install common Node.js tools
+RUN npm install -g \
+    typescript \
+    ts-node \
+    prettier \
+    eslint
+
+# Set workspace
+WORKDIR /workspace
+
+# Keep container alive for docker exec commands
+CMD ["tail", "-f", "/dev/null"]