docs(remediation): fix D-18 overclaim (D-20) — reviewer empirically disproved my own documentation

rev-974 blocked #1027 a second time, and the defect was in this file, not the code.

D-18's AC2 restatement omitted the accidental/independent scope D-19 made mandatory,
and D-18 asserted the tampered-manifest control turns integrity 'from a claim into a
property'. It does not and cannot — that sentence predated D-19 and was never revised
when D-19 landed. rev-974 disproved it by experiment: a same-UID consistent
manifest+marker rewrite passed preflight.

Two banked findings firing on the orchestrator at once: the integrity-claim corollary
(I wrote a claim in the voice of a property, in the document defining the rule against
it), and D-14 propagation — I carried D-19's consequence forward into the charter and
the delivery conditions but never back into the finding it superseded. Backwards
propagation is the same defect as forwards and I did not audit for it.

Corrected in place with the original wording quoted and the disproof recorded, not
silently rewritten.

RM-02 fifth clause: documentation asserting a security or integrity property is itself
a claim requiring a negative control observed red. Prose is not exempt from the
mission's evidentiary standard, and governing prose least of all.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>

docs/remediation/TASKS.md

@@ -93,6 +93,48 @@ and must not be cited as merge evidence. Rely on reviewer clearance + real CI.
 Three independent live instances in a single session — format gate, agent context reset, queue guard —
 is the class confirmed, not anecdote.
 
+### D-20 — the orchestrator's own documentation overclaimed, and a reviewer disproved it empirically
+
+`rev-974` blocked PR #1027 a second time. **The defect was not in the code — it was in this file**, at
+D-18's entry, written by the orchestrator.
+
+Two faults, both mine:
+
+1. **D-18's AC2 restatement omitted the scope clause** that D-19 later established as mandatory
+   ("within an accidental/independent-mutation threat model").
+2. **D-18 asserted that the tampered-manifest control turns integrity "from a claim into a property."**
+   It does not, and _cannot_. That sentence was written **before** D-19 proved the property impossible
+   at this layer, and was never revised when D-19 landed.
+
+**The reviewer did not merely read it — it disproved it.** It performed a **same-UID consistent
+manifest + marker rewrite**, and **preflight passed**. My documented claim was falsified by experiment.
+Code, README, scratchpad and PR body all stated both threat-model directions correctly; **this file was
+the only place still overclaiming.**
+
+**This is two banked findings firing on the orchestrator at once:**
+
+- **The integrity-claim corollary** — I wrote an integrity _claim_ in the voice of an integrity
+  _property_, in the very document that defines the rule against doing so.
+- **D-14 (propagation)** — D-19 superseded D-18's assertion. I propagated the consequence into the
+  charter and the delivery conditions, but **not back into D-18 itself.** A ruling that fails to
+  propagate _backwards_ into the finding it supersedes is the same defect as one that fails to
+  propagate forwards, and I did not audit for that direction.
+
+**Corrected in place**, with the original wording quoted and the empirical disproof recorded, rather
+than silently rewritten — the same standard demanded of any restated criterion.
+
+**Requirement on RM-02 (fifth clause).** Documentation asserting a _security or integrity_ property is
+itself a claim requiring a negative control. Where a document states "X is guaranteed", the registry
+must hold a case that **fails if X is not guaranteed** — and that case must have been observed red.
+**Prose is not exempt from the mission's own evidentiary standard**, and prose in the _governing_
+document least of all: it is the artifact most likely to be quoted as authority long after the code has
+moved on.
+
+**Reviewer credit.** rev-974 was briefed that its highest-priority check was "confirm the PR claims no
+more than it can deliver, and a softened or omitted boundary is a finding even though the code works."
+It applied that instruction **to the orchestrator's own governing document** and produced an experiment
+to settle it. That is the review standard this mission is trying to make ordinary.
+
 ### D-19 — an integrity property that cannot exist at the layer it was specified
 
 Implementing D-18's manifest, the seat + a Codex security review reached **CWE-345**: the symlink
@@ -173,16 +215,30 @@ still rejected as a symlink; descendants are rejected unless _exactly_ certified
 publishes atomically. Strictly **stronger** than blanket rejection — it also catches a **retargeted**
 symlink, which blanket rejection cannot distinguish from a legitimate one.
 
-**AC2 restated (recorded, not absorbed).** _Generated state must reject `.next` itself being a symlink,
-and must reject any descendant symlink not exactly certified by the build manifest — added, removed,
-retargeted, or manifest-tampered all fail with exit 43._
+**AC2 restated (recorded, not absorbed).** _Generated state must reject `.next` itself being a symlink
+or non-directory, and must reject any descendant symlink not exactly certified by the build manifest —
+added, removed, retargeted, or manifest-only-tampered all fail with exit 43 — **within an accidental /
+independent-mutation threat model.**_
+
+> ⚠ **This entry is superseded in part by [D-19](#d-19). Do not read D-18 standalone.** The scope clause
+> above is load-bearing: the design **cannot** defend against a same-UID actor, which can rewrite the
+> manifest and the marker consistently (CWE-345). D-18 was written **before** that impossibility was
+> established.
 
 **Hardening required before this counts.** The manifest is itself generated state, so **a manifest
 writable by whoever plants a rogue symlink certifies the attack** — that is the one way this design
 fails. It must sit inside the same ownership/fingerprint envelope, published atomically via the existing
 marker mechanism, with negative controls **observed red first** for: added, removed, retargeted,
-**manifest-tampered**, plus a positive control that the canonical build passes. The tampered-manifest
-control is non-negotiable; without it, integrity is a claim rather than a property.
+**manifest-only-tampered**, plus a positive control that the canonical build passes.
+
+> ⚠ **CORRECTED (D-20).** This paragraph originally ended: _"without it, integrity is a claim rather
+> than a property."_ **That overclaimed**, by implying the control makes integrity a _property_. It does
+> not, and cannot. The manifest-only-tamper control detects **independent** mutation of the manifest;
+> it confers **no authenticity** against an actor who rewrites manifest _and_ marker together.
+> `rev-974` disproved the original wording empirically — a same-UID consistent manifest+marker rewrite
+> **passed preflight**. Integrity here remains a scoped **drift-detection** property, never an
+> authenticity one. See D-19 and the charter principle on properties that cannot exist at their
+> specified layer.
 
 **Requirement on RM-02 (fourth clause).** The registry must detect **conflicts between registered
 criteria**, not only wrongness and coverage. Two criteria that cannot simultaneously hold is a registry