* feat(plugins): add post-user-turn display hooks

* feat(plugins): expose usage to command actions

* feat(usage): track top-level turn ledgers

* chore: bump version to 0.10.1

* heredocs constant change

* improve highlights, model defaults

* update tests

* fix(acp): stub user_turn_usage on plugin command tests

Plugin command context now reads app.user_turn_usage; keep the ACP
slash-command stub in sync so switch/refresh integration coverage runs.

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Co-authored-by: evalstate <evalstate@users.noreply.github.com>