Persist bash history and bake shell quality-of-life defaults

Two changes that address a longstanding frustration: bash history is
lost on every container recreate, and the container's ~/.bashrc and
~/.inputrc are stock Debian (no history tuning, no prefix search on
arrow keys, no integrations).

Added a named volume 'devbox-shell-history' mounted at ~/.cache/bash
with HISTFILE pointing there; history now survives 'docker compose up
--force-recreate'. The volume is added to both docker-compose.yml and
docker-compose.shared.yml, and ~/.cache/bash is registered in the
entrypoint ownership-fix loop per the AGENTS.md convention.

Baked rootfs/home/developer/.bash_aliases (sourced automatically by
Debian's default ~/.bashrc) and rootfs/home/developer/.inputrc into
the image. They give new containers: 100k-entry timestamped dedup
history with per-prompt flush, Up/Down arrow prefix history search,
case-insensitive coloured completion, aliases that prefer eza and
bat when present, git shortcuts, interactive rm/mv/cp, zoxide and
fzf (via 'fzf --bash') integration, and a [devbox] prompt marker.
The fzf integration uses 'fzf --bash' because we install fzf from
GitHub releases, not apt — the apt-path key-bindings aren't present.

Users who prefer their host's own shell config can uncomment two
commented bind-mount lines in docker-compose.yml to shadow the
baked defaults.

Dockerfile

@@ -200,9 +200,19 @@ RUN mkdir -p /workspace \
     /home/${USER_NAME}/.config/opencode/skills \
     /home/${USER_NAME}/.agents/skills \
     /home/${USER_NAME}/.local/share/opencode \
+    /home/${USER_NAME}/.cache/bash \
     /home/${USER_NAME}/.ssh && \
     chown -R ${USER_NAME}:${USER_NAME} /workspace /home/${USER_NAME}
 
+# ── Shell defaults (bash history, aliases, readline) ─────────────────
+# Baked into the image so a fresh container has sensible history and
+# readline behaviour out of the box. Users can override by bind-mounting
+# their host ~/.inputrc or ~/.bash_aliases via docker-compose.yml.
+# History itself persists via the devbox-shell-history named volume
+# mounted at ~/.cache/bash (HISTFILE points there).
+COPY --chown=${USER_UID}:${USER_GID} rootfs/home/developer/.bash_aliases /home/${USER_NAME}/.bash_aliases
+COPY --chown=${USER_UID}:${USER_GID} rootfs/home/developer/.inputrc      /home/${USER_NAME}/.inputrc
+
 # ── Entrypoint ────────────────────────────────────────────────────────
 COPY entrypoint.sh /usr/local/bin/entrypoint.sh
 COPY entrypoint-user.sh /usr/local/bin/entrypoint-user.sh