docs: residual handoff in hub docs, AGENTS, and templates

Align agent close/workplan finish with fleet residual convention
(live work records, origin residual + origin_ref). Reference pages for
work-records and intakes; session and workplan templates updated.

scripts/project_rules/workplan-convention.template

@@ -38,6 +38,22 @@ state_hub_task_id: "<uuid>"         # written by fix-consistency — do not edit
 Status progression is `todo` → `progress` → `done`; use `wait` for waiting or
 blocked work and `cancel` for stopped work.
 
+### Residuals (role, not kind)
+
+When finishing a workplan, **actionable leftovers must become live work
+records** before `status: finished`. Residual is not a registered kind and
+must not be parked only in `SCOPE.md` or finished-file prose.
+
+| Shape | Capture as | Links |
+| --- | --- | --- |
+| Small Green/Blue parkable | intake (queue YAML / `*-IN-*`) | `origin: residual`, `origin_ref: {WP_PREFIX}-NNNN` |
+| Multi-step | next workplan | name parent WP; optional promote from residual intake |
+| Founder gate / time | decision / engagement | same origin fields when from residual intake |
+
+Fleet listing of residuals is a State Hub concern (`list_intakes` + origin
+filters; planned `statehub residuals`). Canon:
+`the-custodian/canon/standards/work-record-types_v0.1.md` § Residuals.
+
 Workplan frontmatter carries `state_hub_workstream_id` — a legacy field name
 kept for compatibility; it holds the hub workplan UUID and is written by
 fix-consistency. Do not edit or rename it.