feat(terminology): prose sweep tool and custodian workplan cleanup (CUST-WP-0055 T04)

Add sweep_workstream_prose.py for agent-guidance files, sweep active workplan
prose in-repo, tighten scan allowlist exclusions, and update ADR-001 closure
protocol to workplan-first terminology.

workplans/CUST-WP-0000b-state-hub-v0.2-decisions-dependencies.md

@@ -12,7 +12,7 @@ updated: "2026-02-25"
 completed: "2026-02-25"
 state_hub_workstream_id: "6585ee66-aa4e-436e-bbec-d83293c33e8f"
 note: >
-  Pre-ADR-001 record. This workstream was created DB-first before the
+  Pre-ADR-001 record. This workplan was created DB-first before the
   workplan-as-repository-artefact convention was established. Retroactive
   file written on 2026-03-11 to satisfy the ADR-001 consistency checker (C-08).---
 
@@ -24,11 +24,11 @@ Delivered 2026-02-25, evolving the hub from a state tracker to an active
 coordination layer:
 
 - `WorkstreamDependency` model + migration `0b547c153153` — directed
-  dependency graph between workstreams
+  dependency graph between workplans
 - API: `POST/GET /workstreams/{id}/dependencies/`,
   `DELETE /workstreams/{id}/dependencies/{dep_id}`
 - API: `GET /state/next_steps` — derived next-action suggestions (never persisted)
-- `StateSummary` extended with `next_steps` and `depends_on`/`blocks` on workstreams
+- `StateSummary` extended with `next_steps` and `depends_on`/`blocks` on workplans
 - Design boundary formalised: hub is a read model with exactly two write use
   cases — resolving decisions and suggesting next steps
 - MCP: `get_next_steps()` tool added