docs(qa): name the legacy grant in platform-owner-email-anchor clause 6

Seat review nit on the re-author: clause 6 opened with "the legacy grant
is an anchor under single ONLY" and then said an organization-less row
anchors nothing, which reads as a contradiction. The clause now names the
legacy grant as the admin_full_access grant first-registrant promotion
writes, owned by the Default Organization, as opposed to the config anchor.

Claude-Session: https://claude.ai/code/session_01JDXz1o5fLjTiZcUdKvNKJN
Co-authored-by: Claude <noreply@anthropic.com>

Author: claude

docs/qa/platform-checklist/areas/access-security.json

@@ -2976,7 +2976,7 @@
           "evidence": "test output (and, when the fixture exists, M's entitled traces)"
         },
         {
-          "clause": "the legacy grant is an anchor under single ONLY, and silently so (#11663 L5): under single, standing resting on the admin_full_access grant first-registrant promotion writes — owned by the Default Organization (ADR-0131 D5) — alone still resolves PLATFORM_ADMIN (clauses 1 and 3 observe it live as the seeded admin's 200); an organization-less admin_full_access row anchors nothing on any posture; under a walled posture — postureEnforcesWall, i.e. every posture except single, read from the REQUESTED posture — the same grant confers no PLATFORM_ADMIN standing (the held set still grants its own capabilities in its own organization; only the rung and the built-in platform_admin position go), while the config anchor keeps conferring on that same walled rig; and the request path logs nothing about the row on any posture",
+          "clause": "the legacy grant — the admin_full_access grant first-registrant promotion writes, owned by the Default Organization (ADR-0131 D5), as opposed to the config anchor — is an anchor under single ONLY, and silently so (#11663 L5): under single, standing resting on that grant alone still resolves PLATFORM_ADMIN (clauses 1 and 3 observe it live as the seeded admin's 200); an organization-less admin_full_access row anchors nothing on any posture; under a walled posture — postureEnforcesWall, i.e. every posture except single, read from the REQUESTED posture — the same grant confers no PLATFORM_ADMIN standing (the held set still grants its own capabilities in its own organization; only the rung and the built-in platform_admin position go), while the config anchor keeps conferring on that same walled rig; and the request path logs nothing about the row on any posture",
           "oracle": "test",
           "verify": "packages/core/src/security/resolve-authz-context.platform-admin-config.test.ts — the '[#11663 L5] the legacy grant row is an anchor under `single`, and NOWHERE else', '[#11663 L5] the legacy anchor confers only on the rigs Choice 4A keeps it for' and '[#11663 L5] standing across postures' describes, and the '[ADR-0131 D5] under `single` the Default Organization's admin_full_access grant is the anchor' describe (the Default Organization's grant confers with no config; another organization's grant, a walled rig and the organization-less row a pre-D5 promotion wrote anchor nothing); packages/core/src/security/platform-admin.test.ts — '[#11663 L5] the legacy-grant deprecation pointer is retired' (both pointer symbols absent from the module and from the @objectstack/core security entry, with positive controls). The single half's fate was #11979's (Choice 4B): it landed (PR #24373), and this clause was re-authored for it at revision 8 rather than read as a regression",
           "evidence": "test output"