Per-step install_step counts, SPLIT BY PLATFORM, over a declared window (default 7 days).

Shape (lmcp-admin #153): {window_days, platforms: {darwin|windows|other: {total_installs, steps: [{step, installs, ok, fail}]}}}. All three platform keys are always present (empty when a platform had no install in the window). steps lists every step the events carry, in _INSTALL_STEP_SEQ order (unknown last), so the card holds no second list. total_installs is the max step count within the platform (the card's 100% base — no dependency on a start step); it is NOT a distinct-install count, and ok + fail need not equal installs (an identity may be in both, and statuses other than ok/fail are in neither) — label it as a base, not as installs.

Identity is the install, not the machine: early install.sh steps fire before a machine_id exists but carry a fingerprint, so count DISTINCT COALESCE(machine_id, fingerprint). Test machines excluded; ok/fail split by status.