docs: tighten license summary and README per counsel

Author: flyingrobots

LICENSE

@@ -1,10 +1,20 @@
-Licensing summary
+SPDX-License-Identifier: Apache-2.0
+This project is dual-licensed. Different parts of the repository are covered
+by different license options, as follows:
 
-- Code (all source, build scripts, tooling, binaries): Apache License 2.0 only.  
-  See `LICENSE-APACHE` or https://www.apache.org/licenses/LICENSE-2.0
+1. Code (all source, build scripts, tooling, binaries)
+   - Licensed under the Apache License, Version 2.0 only.
+   - See `LICENSE-APACHE` or https://www.apache.org/licenses/LICENSE-2.0
 
-- Theory / math / docs corpus (e.g., `docs/`, `rmg-math/`, papers/notes): dual-licensed  
-  under Apache 2.0 OR MIND-UCAL v1.0, at your option.  
-  See `LICENSE-APACHE` and `LICENSE-MIND-UCAL` (canonical text in ../universal-charter/MIND-UCAL/LICENSE).
+2. Theory / math / documentation corpus (e.g., `docs/`, `rmg-math/`, papers/notes)
+   - Dual-licensed under:
+       (a) Apache License, Version 2.0, OR
+       (b) MIND-UCAL License v1.0
+   - See `LICENSE-APACHE` and `LICENSE-MIND-UCAL` (canonical text in ../universal-charter/MIND-UCAL/LICENSE).
+
+You may use the theory / math / documentation under EITHER Apache-2.0 OR
+MIND-UCAL v1.0, at your option. If you do not wish to use MIND-UCAL, you may
+use all such materials under Apache-2.0 alone. No portion of this repository
+requires adopting MIND-UCAL.
 
 Unless required by applicable law or agreed to in writing, material is provided on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND.

README.md

@@ -1,3 +1,4 @@
+SPDX-License-Identifier: Apache-2.0 OR MIND-UCAL-1.0
 # Echo
 
 ```rust
@@ -339,4 +340,8 @@ Licensing split:
 - Code (all source/build/tooling): Apache 2.0 — see `LICENSE-APACHE`
 - Theory / math / docs corpus: Apache 2.0 OR MIND-UCAL v1.0 — see `LICENSE-MIND-UCAL`
 
+If you do not wish to use MIND-UCAL, you may freely use all theory, math, and
+documentation under Apache 2.0 alone. No part of this repository requires
+adopting MIND-UCAL.
+
 See `LICENSE` for the summary and `NOTICE` for attribution.