add docs/governance/CHANGE_CONTROL.md — receipt-update triggers and standing rule

This document outlines the rules for updating receipts and claim boundaries in response to code or claim changes. It specifies triggers for updates and clarifies what does not require a receipt entry.

Author: LalaSkye

docs/governance/CHANGE_CONTROL.md

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+# CHANGE CONTROL
+
+Short rule file for when claim or invariant changes require a receipt update.
+
+This file governs **when** documentation must be updated alongside a code or claim change. It is intentionally short. The PR template enforces the checklist; this file defines the triggers.
+
+---
+
+## Triggers requiring a BUILD_RECEIPTS.md update
+
+A receipt entry **must** be added to `docs/governance/BUILD_RECEIPTS.md` when a commit:
+
+1. Adds, removes, or modifies an invariant in `INVARIANTS.md`
+2. Adds, removes, or modifies an adversarial vector in `INVARIANT_TEST_VECTORS_v1.json`
+3. Changes the behaviour of `scripts/verify_adversarial_invariants.py`
+4. Adds, removes, or modifies a claim in `ADMISSIBLE_CLAIM_REGISTER_v1.md`
+5. Changes the CI workflow in a way that affects enforcement scope
+6. Changes the PR template in a way that affects contributor obligations
+
+---
+
+## Triggers requiring a claim-boundary review
+
+The standing claim boundary **must** be re-stated (not silently widened) when a commit:
+
+1. Promotes a configured surface to an evidenced one (e.g. CI green proof)
+2. Adds a new proof surface visible from README or entry
+3. Removes or weakens an existing proof surface
+
+---
+
+## Triggers NOT requiring a receipt update
+
+To prevent ledger bloat, the following do **not** require a receipt entry:
+
+- Typo fixes
+- Formatting-only changes
+- Internal comments and docstrings without behavioural change
+- Dependency bumps that do not affect verifier output
+
+---
+
+## Receipt entry shape
+
+Each receipt entry in `BUILD_RECEIPTS.md` should record:
+
+- Commit SHA (short)
+- File(s) affected
+- Structural layer
+- What is now held
+- What is still not held
+- Safe claim
+
+---
+
+## Standing rule
+
+*No claim is upgraded without an evidenced trigger. No surface is widened without a receipt. The boundary is re-stated, never assumed.*