Add neovim 0.12, bat, eza, zoxide, tmux, htop to base image

Replace vim-tiny with neovim from GitHub releases (pinned, multi-arch).
Add bat, eza, zoxide from GitHub releases and tmux, htop, patch from apt.
Move tmux from OMOS-only to base image. Set EDITOR=nvim.
Add neovim config mount option to docker-compose and docs.

Dockerfile

@@ -27,7 +27,10 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     fd-find \
     tree \
     less \
-    vim-tiny \
+    htop \
+    tmux \
+    patch \
+    diffutils \
     sudo \
     locales \
     procps \
@@ -59,11 +62,39 @@ RUN ARCH=$(case "${TARGETARCH}" in amd64) echo "amd64" ;; arm64) echo "arm64" ;;
     git lfs install --system && \
     git-lfs --version
 
+# neovim — modern text editor (pre-built release from GitHub)
+ARG NVIM_VERSION=0.12.1
+RUN ARCH=$(case "${TARGETARCH}" in amd64) echo "x86_64" ;; arm64) echo "arm64" ;; *) echo "x86_64" ;; esac) && \
+    curl -fsSL "https://github.com/neovim/neovim/releases/download/v${NVIM_VERSION}/nvim-linux-${ARCH}.tar.gz" | tar -xz -C /opt && \
+    ln -s /opt/nvim-linux-${ARCH}/bin/nvim /usr/local/bin/nvim && \
+    nvim --version | head -1
+
+# bat — syntax-highlighted cat replacement
+ARG BAT_VERSION=0.25.0
+RUN ARCH=$(case "${TARGETARCH}" in amd64) echo "x86_64" ;; arm64) echo "aarch64" ;; *) echo "x86_64" ;; esac) && \
+    curl -fsSL "https://github.com/sharkdp/bat/releases/download/v${BAT_VERSION}/bat-v${BAT_VERSION}-${ARCH}-unknown-linux-musl.tar.gz" | tar -xz -C /tmp && \
+    install /tmp/bat-v${BAT_VERSION}-${ARCH}-unknown-linux-musl/bat /usr/local/bin/bat && \
+    rm -rf /tmp/bat-v${BAT_VERSION}-* && \
+    bat --version
+
+# eza — modern ls replacement
+ARG EZA_VERSION=0.23.4
+RUN ARCH=$(case "${TARGETARCH}" in amd64) echo "x86_64" ;; arm64) echo "aarch64" ;; *) echo "x86_64" ;; esac) && \
+    curl -fsSL "https://github.com/eza-community/eza/releases/download/v${EZA_VERSION}/eza_${ARCH}-unknown-linux-gnu.tar.gz" | tar -xz -C /usr/local/bin && \
+    eza --version | head -1
+
+# zoxide — smarter cd command
+ARG ZOXIDE_VERSION=0.9.9
+RUN ARCH=$(case "${TARGETARCH}" in amd64) echo "x86_64" ;; arm64) echo "aarch64" ;; *) echo "x86_64" ;; esac) && \
+    curl -fsSL "https://github.com/ajeetdsouza/zoxide/releases/download/v${ZOXIDE_VERSION}/zoxide-${ZOXIDE_VERSION}-${ARCH}-unknown-linux-musl.tar.gz" | tar -xz -C /usr/local/bin zoxide && \
+    zoxide --version
+
 # Set locale
 RUN sed -i '/en_US.UTF-8/s/^# //g' /etc/locale.gen && locale-gen
 ENV LANG=en_US.UTF-8
 ENV LANGUAGE=en_US:en
 ENV LC_ALL=en_US.UTF-8
+ENV EDITOR=nvim
 
 # ── Node.js (required for opencode v1.x install + MCP servers) ──────
 ARG NODE_VERSION=22
@@ -107,13 +138,11 @@ RUN if [ "${INSTALL_GO}" = "true" ]; then \
     fi
 
 # ── Optional: oh-my-opencode-slim (multi-agent orchestration) ────────
-# Installs Bun runtime, tmux, and the oh-my-opencode-slim npm package.
+# Installs Bun runtime and the oh-my-opencode-slim npm package.
 # Runtime activation is controlled by ENABLE_OMOS env var in entrypoint.
 ARG INSTALL_OMOS=false
 ARG OMOS_VERSION=latest
 RUN if [ "${INSTALL_OMOS}" = "true" ]; then \
-      apt-get update && apt-get install -y --no-install-recommends tmux && \
-      rm -rf /var/lib/apt/lists/* && \
       curl -fsSL https://bun.sh/install | BUN_INSTALL=/usr/local bash && \
       bun --version && \
       npm install -g oh-my-opencode-slim@${OMOS_VERSION}; \