Add intent-is-the-source-of-truth principle; align README-Driven Context

Author: MariusStorhaug

src/docs/Ways-of-Working/Principles/Engineering-Practices.md

@@ -47,6 +47,12 @@ Documentation describes the system as it **is**, in the present tense — not th
 
 This governs this site, every README, and every specification — and it is why a pull request description states what the change *contributes*, not the steps taken to produce it.
 
+## Intent is the source of truth
+
+The documented intent that lives in the default branch — the specs, the docs, the issue descriptions — is the source of truth for what the system is meant to be. The implementation is a *representation* of that intent: the running code is what the system currently is, not necessarily what it should be.
+
+Either can be wrong. The intent may be mistaken, stale, or unclear; the implementation may have drifted from a correct intent. So when the two disagree, do not assume which is at fault — **diagnose it**: is the intent wrong (fix the doc, spec, or issue), or is the implementation wrong (fix the code)? Update whichever is wrong so the two converge again. A mismatch is a signal to reconcile, not a reason to silently trust the code or blindly rewrite the doc.
+
 ## Test-driven development
 
 Define the tests when you define the behavior. Update them when behavior changes. Tests are the executable specification.

src/docs/Ways-of-Working/Readme-Driven-Context.md

@@ -12,7 +12,7 @@ The README is the **evergreen context document** for every repository in the MSX
 - **The README is the front door.** Anyone — human or agent — encountering the repository for the first time should understand the purpose, scope, and current capabilities from the README without reading source code.
 - **The README is evergreen.** It is a living document that always reflects the current state of the repository. When functionality is added, changed, or removed, the README is updated in the same unit of work.
 - **Documentation is not optional.** A feature that is not documented in the README is effectively invisible. Updating the README is part of completing the work, not a follow-up task.
-- **The README is authoritative.** If the README and the code disagree, the README is out of date and must be corrected — but it remains the intended source of truth.
+- **The README is authoritative, but not automatically right.** It is the intended source of truth, yet a README can be wrong just as code can. When the README and the code disagree, [diagnose which is wrong](Principles/Engineering-Practices.md#intent-is-the-source-of-truth) — correct the README if the intent drifted, or fix the code if it diverged — so the two converge.
 
 ## What belongs in the README