Reconcile no-add-content constraint with defining undefined terms

Address the internal contradiction between the "do not add or remove content"
constraint and the requirement to eliminate undefined terms on first use.

- revise-for-readability: clarify Non-Goals so a minimal definition or acronym
  expansion that restates existing meaning counts as prose revision, not new
  content
- readability-revision-workflow: plain-language rule 4 now allows definitions
  only when they restate meaning already present; otherwise the undefined term
  is recorded as a residual issue

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: abeltrano

protocols/reasoning/readability-revision-workflow.md

@@ -101,7 +101,10 @@ Plain-language rules:
 1. One idea per sentence. Split a sentence that carries more than one.
 2. Front-load the point. State the conclusion or action first, then the detail.
 3. Prefer the plain word ("use" over "utilize", "help" over "assist").
-4. Define a needed term or expand an acronym on first use.
+4. Define a needed term or expand an acronym on first use, but only by restating
+   meaning already present in or established by the document. If a correct
+   definition would introduce information not derivable from the source, do not
+   invent it — record the undefined term as a residual issue instead.
 5. Vary sentence length so the rhythm is not a drone.
 6. Keep terminology consistent — one term per concept, not a rotation of
    synonyms.

templates/revise-for-readability.md

@@ -96,8 +96,11 @@ prose becomes short, direct, plain prose; technical meaning stays exact.
   edit the prose around them.
 - Do NOT rewrite code, data, tables, diagrams, quoted text, or format
   scaffolding.
-- Do NOT restructure the document, reorder sections, or add or remove content;
-  this task revises prose, it does not redesign the document.
+- Do NOT restructure the document, reorder sections, or add or remove
+  substantive content or claims; this task revises prose, it does not redesign
+  the document. Adding a minimal definition or acronym expansion that restates
+  meaning already present in the source counts as prose revision, not new
+  content.
 - Do NOT report an estimated Flesch score as a computed one, and do NOT claim a
   readability gain without a before/after comparison.