docs: AI Principles restructured + Compliance Matrix + Platform governance + RFC-001 Button

- AI_DESIGN_PRINCIPLES.md:
  - Restructured into 5 parts: A. Decision Process, B. Component Selection,
    C. Token Usage, D. Design Review, E. Escalation
  - All rules use RFC 2119 normative words (MUST/MUST NOT/SHOULD/MAY)
  - Clearer escalation path: when to create DDR, when to flag uncertainty

- COMPLIANCE_MATRIX.md:
  - Tracks readiness for all 29 components (Tier 1/2/3)
  - 6 dimensions: Governance, Tokens, Motion, Accessibility, AI, QA
  - Foundation documents tracked separately
  - Button at 82% (reference for others)

- docs/platform/README.md:
  - Reserved directory for cross-cutting governance
  - Future: AI Governance, Product Governance, Review Process,
    Quality Gates, Release Governance, Decision Frameworks
  - Separates platform governance from design system

- LANDVEX_DESIGN_SPECIFICATION.md:
  - Button renamed to RFC-001: Canonical Button Component
  - Structured with: Cognitive Purpose, When to Use/NOT Use,
    User Expectation, Interaction Contract, Failure Behaviour,
    Accessibility Contract, AI Contract
  - Sets standard for all future RFC component specs

Rationale: AI rules before components (AI writes components).
Compliance matrix makes progress visible. Platform governance
separates cross-cutting concerns from design system. RFC format
for components ensures production-ready specifications.

docs/design/LANDVEX_DESIGN_SPECIFICATION.md

@@ -772,56 +772,76 @@ Only then may a new component be defined.
 
 > **Princip:** Varje komponent har en egen specifikation med states, ARIA, keyboard, touch, animation och acceptance criteria.
 
-### 8.3.1 Button
+### RFC-001: Canonical Button Component
 
-**Cognitive Purpose:** Button exists to trigger actions that modify state or advance workflow. It is the primary interface between user intent and system response.
+**Status:** ✅ Approved as reference implementation
+**Tier:** 1 (Canonical)
+**Inherits From:** — (root component)
+
+---
+
+#### Cognitive Purpose
+
+Button exists to trigger actions that modify state or advance workflow. It is the primary interface between user intent and system response.
+
+#### When to Use
 
-**When to use:**
 - Primary user action (submit, confirm, save)
 - Form submission
 - Dialog confirmation
 - Action that requires explicit user commitment
 
-**When NOT to use:**
+#### When NOT to Use
+
 - Navigation (use Link)
 - Toggling state (use Switch)
 - Selecting from options (use Select)
 - Secondary information reveal (use Accordion)
 
-**User Expectation:**
+#### User Expectation
+
 - Button is clickable
 - Button responds immediately to press
 - Button indicates if action is in progress
 - Button indicates if action is unavailable
 
-**Interaction Contract:**
-- Click → Action executes
-- Hover → Visual feedback (but action does not execute)
-- Focus → Keyboard can activate
-- Loading → Action is in progress, further clicks ignored
-- Disabled → Action is unavailable, reason explained elsewhere
+#### Interaction Contract
 
-**Failure Behaviour:**
-- If action fails: Button returns to default state, error shown elsewhere (not on button)
-- If network fails: Button remains in loading state until timeout, then error
-- If validation fails: Button remains enabled, form shows errors
+| Event | Response |
+|-------|----------|
+| Click | Action executes |
+| Hover | Visual feedback only |
+| Focus | Keyboard can activate |
+| Loading | Further clicks ignored |
+| Disabled | Action unavailable |
+
+#### Failure Behaviour
+
+| Scenario | Response |
+|----------|----------|
+| Action fails | Button returns to default, error shown elsewhere |
+| Network fails | Button remains loading until timeout, then error |
+| Validation fails | Button remains enabled, form shows errors |
+
+#### Accessibility Contract
 
-**Accessibility Contract:**
 - Screen reader announces button role and label
 - Focus is visible and logical
 - Disabled state is communicated
 - Loading state is communicated
 
-**AI Contract:**
-- AI chooses Button for primary actions
-- AI chooses Link for navigation
-- AI chooses Icon Button for toolbar actions
-- AI chooses Split Button for primary + secondary options
-- AI never uses Button for navigation
+#### AI Contract
+
+| Scenario | AI Choice |
+|----------|-----------|
+| Primary action | Button |
+| Navigation | Link |
+| Toolbar action | Icon Button |
+| Primary + secondary options | Split Button |
 
 ---
 
-**Token Dependencies:**
+#### Token Dependencies
 - `button-primary-bg` → `brand-500`
 - `button-primary-bg-hover` → `brand-600`
 - `button-primary-text` → `text-inverse`