DOCS-009: ADR status and supersession-banner hygiene batch

[mlorentedev]

Source: docs audit 2026-07-07 (docs/audits/docs-audit-2026-07-07.md) — findings D10, D20, D25, D26 (CONFIRMED).

One PR, status-only edits (the convention already exists — ADR-001/008/014/020 model it):

• ADR-009 status: proposed → accepted (AGENTS.md SSOT fully live, guarded by tests/agents-md.bats).
• ADR-029 status: proposed → accepted (dotf secrets sync shipped, v0.29.0, cli/internal/cmd/secrets_sync.go).
• ADR-002 / ADR-005: add "partially superseded by ADR-028/030" banners (ambient-load reversed; secrets_add/dotfiles-sync era retired).
• ADR-006: add the ADR-012 supersession banner (copy-not-symlink); ADR-016: add the ADR-026 banner (slice directionality).
• ADR-021: mark stale "(in progress)" noun markers as shipped; add an amendment noting the eval "$(dotf secrets env)" shim plan was reversed by ADR-028 (no-ambient).
• ADR-012: the dot alias named as the retraining mitigation does not exist — amend or drop.
• ADR-007: one-line pointer that the MCP server table predates the 2026-05-25 removal (mcp-servers.json _history is current).
• ADR-028 §Ratification: "escrow not yet built" — now built (feat(secrets): dotf secrets backup DR escrow (ADR-028) #661, secrets_backup.go); one-line addendum.
• audit-007 frontmatter status: active → dated-snapshot status (plan half-executed since 2026-06-20).