docs(adr): correct the ADR-0018 inert-inputs claims in pointer form (#369)

[brenpike]

Summary

Corrects the superseded claims in ADR-0018's 2026-05-31 inert inputs-file navigator implementation note, without rewriting the original body.

• Adds a scoped supersession note under the 2026-05-31 note heading. It points at plugin/governance/security-policy.md ("Inert Inputs-File Navigator Pattern") and at the new amendment.
• Appends a 2026-09-25 amendment. It corrects four claims: the "Inert content" absolute (withdrawn as an over-claim), the retired singleton transport paths, the "All three pipeline navigators" count, and the spawn-brood transport exemption recorded in the 2026-06-01 amendment.
• Item 5 states a standing rule: every path, version number, count, membership list and named mechanism in this ADR's notes and amendments is a dated snapshot, not authority. Readers take current values from the live source.

The corrections are in pointer form. Each item names the superseded claim and the live document that owns the subject, and restates no current value. Local review showed that every copied value became the next stale-literal finding, so the correction text now carries none. No line that exists on main is modified; the diff is insertions only.

Closes #369.

Validation

• bash tools/validate.sh --changed: policy_check.sh --strict PASS, 0 new findings (docs/adr/* maps to the policy suite).
• Local Codex review (4 iterations): fixed findings on the navigator enumeration, the inherited brood-manifest literals, and the live-value restatements. A final finding asked for section-level pointers into ADR-0021 and plugin/references/brood-ledger-model.md instead of whole-document pointers. It was accepted as a residual, because those section headings carry ordinals and a schema version literal, which would bring back the stale-literal class.

Versioning

Docs-only (docs/adr/**). No plugin runtime change, no version bump, no CHANGELOG entry.

Follow-ups

• ADR-0019: brood-manifest amendment still names manifest_version 3 and the removed liveness guard #375: ADR-0019's brood-manifest amendment carries the same stale manifest_version: 3 and liveness-guard claims. It is deferred because that file is out of this PR's scope.

[chatgpt-codex-connector]

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