Swarm-level companion to the per-agent favorite-tools doughnut (#1433).
Aggregates each agent's bash_commands(ts, head) table (written by
hive-bash-mcp) across the whole hive and surfaces the top-10 most-run
command heads on the dashboard ST4TS tab, alongside the existing model
mix.
- hive_stats.rs: AgentAgg gains a `bash` head→count map, filled by a new
guarded `read_bash_heads()` that reuses read_agent's read-only
connection. A missing `bash_commands` table (capture hasn't run for
that agent) or any read error yields an empty map — isolated from
read_agent's error path so it never drops an agent from the rollup.
HiveStats gains `bash_mix: Vec<KeyCount>` (busiest-first, top 10).
Unit tests cover the per-head tally + window cutoff and the
missing-table degrade-to-empty path (in-memory sqlite).
- dashboard: a "favorite tools (bash commands across the swarm)" CSS-bar
list on the ST4TS pane, mirroring the model-mix bars. Header + list
stay hidden until bash_mix has data, so a fresh hive shows no empty
block. (Dashboard ships no chart lib — bars, not a doughnut.)
- docs: dashboard.md ST4TS section documents the new rollup.
Closes#1449. Inert until the hive-bash-mcp capture (#1448, merged) has
recorded data across agents.