Prepare supervision model consumers

[JTInventory]

Summary

• expand the firstmate.supervision.v1 schema so Radar-style displays can consume the nested JSON contract directly
• document the Radar consumer contract and narrow Firstmate skill-root map
• add harness-aware skill invocation guidance to generated briefs and docs
• capture the Radar display boundary as a CE solution note

Validation

• bash -n bin/fm-supervise.sh bin/fm-supervision-model.sh bin/fm-brief.sh
• bash tests/fm-supervision-model.test.sh
• bash tests/fm-tangle-guard.test.sh
• bash tests/fm-secondmate-safety.test.sh
• FM_HOME=/root/firstmate bin/fm-supervise.sh --json --no-default-reminders | python3 -m json.tool >/tmp/fm-supervise-workflow-structure.json
• bin/fm-supervise.sh --schema | python3 -m json.tool >/tmp/fm-supervise-schema-workflow-structure.json
• git diff --check

shellcheck was attempted but is not installed in this environment.

Notes

This is stacked on fm/fm-supervise-impl-0625 because upstream PR kunchenguid#76 is not merged yet.
It intentionally does not edit /root/.local/bin/fm-radar; the exact external Radar patch handoff is in the local task report.