docs(sdlc): public-repo surfaces read as product engineering, not internal governance

Commit messages, code comments and docs ship to readers with no access to how the
work was governed internally, and nothing in the conventions said so.

Adds two forward-only rules: no verbatim internal quotes (especially emotional
ones — quote the technical content of a decision, never the person or the mood),
and no governance framing (write what the change does and why it is correct on its
own terms, not who ruled it or which gate it passed).

States the test rather than a list of banned words: a reader outside the project
should be able to act on the text without knowing any internal role, seat, or
process name.

Not retroactive; existing history is not rewritten for these.

Co-Authored-By: Claude Fable 5 <[email protected]>

docs/reference/sdlc-conventions.md

@@ -122,6 +122,26 @@ The C1 header's five required fields: `slice`, `candidate_sha`,
 - `artifact_type`: `guard | qa | rev1-r1 | rev1-r2 | adjudication`
 - `verdict`: `CLEAR | BLOCKING | CONCERNING | PASS | NOT-CLEAR`
 
+### Public-repo surfaces read as product engineering
+
+Commit messages, code comments, and markdown/docs are **public-repo surfaces**: they
+ship to readers who have no access to — and no interest in — how the work was
+governed internally. Two rules, **forward-only** (existing history is not rewritten
+for these):
+
+- **No verbatim internal quotes**, and especially not emotional or frustrated ones.
+  Quote the *technical content* of a decision, never the person or the mood in which
+  it was made.
+- **No governance framing.** Write what the change does and why it is correct on its
+  own terms — not who ruled it, who approved it, or which internal gate it passed.
+  "The guard fires at lock because a placeholder would otherwise satisfy the join"
+  is product engineering. "X ruled this at the Y gate" is internal governance leaking
+  into a public artifact.
+
+The test: a reader outside the project should be able to act on the text without
+knowing any internal role, seat, or process name. This is the same principle applied
+to attribution and tone rather than to vocabulary.
+
 ### A cited hash STATES WHAT IT COVERS
 
 A hash offered as evidence is only checkable if the reader knows what bytes it