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.

rootfs/home/developer/.inputrc

@@ -0,0 +1,27 @@
+# opencode-devbox readline defaults
+# To override, bind-mount your host's ~/.inputrc over this file
+# via docker-compose.yml.
+
+# Inherit system-wide defaults (colour, 8-bit input, …) if present
+$include /etc/inputrc
+
+# ── History search on Up/Down ────────────────────────────────────────
+# Type a prefix, press Up, and walk through previous commands starting
+# with that prefix. Ctrl-Up / Ctrl-Down keep the unconditional stepper.
+"\e[A": history-search-backward
+"\e[B": history-search-forward
+"\e[1;5A": previous-history
+"\e[1;5B": next-history
+
+# ── Completion quality ───────────────────────────────────────────────
+set show-all-if-ambiguous on      # single Tab shows matches on ambiguity
+set completion-ignore-case on     # case-insensitive file/dir completion
+set colored-stats on              # colour ls-style completion list entries
+set colored-completion-prefix on  # highlight the matched prefix
+set visible-stats on              # append /*@ type indicators in completion
+set mark-symlinked-directories on # add trailing / to symlinks to dirs
+set skip-completed-text on        # don't re-insert already-typed text
+
+# Treat hyphens and underscores as equivalent when completing (e.g.
+# typing `foo-` matches both `foo-bar` and `foo_bar`).
+set completion-map-case on