feat(shared): add Tier 3 components (8 critical for ms-ai-architect Playground v3)

Authored in Claude Code following the design-DNA established by claude.ai/design
in v0.1 (tokens + Tier 1 + Tier 2). Visual coherence verified against existing
components via tier3-preview.html showcase.

shared/playground-design-system/components-tier3.css (~480 lines):
- pair-before-after: ROS/DPIA/AI Act inherent->residual primitive with delta
  pill (improved/worsened); responsive collapse to vertical on narrow viewports
- aiact-timeline: 4 EU AI Act milestones (2025-02-02 .. 2027-08-02) with
  per-system countdown chips (urgent/soon/distant), today-marker, and per-
  milestone passed/active/upcoming states
- tracks: Guide/Explore/Expert 3-track entry pattern carried from Playground v2,
  top-bar color coding per track
- rights-matrix: FRIA 12 EU Charter rights x 5 impact levels (Art. 27 EU AI Act)
- capability-matrix: license x kapabilitet with explicit icons per status
  (available/cost/conditional/missing) - never color-only
- agent-grid + agent-card: parallel-worker status with state pills, progress
  bars, metric chips, pulsing dot for running, distinct failure-red token
- error-summary: Aksel/GOV.UK pattern, white bg + red border + dark body text
  + red heading (NOT large pink fill — fixes contrast bug)
- guide-panel: Aksel friendly inline guidance, info/success/warn variants

Also fixes shared/playground-design-system/base.css inline-message--error which
had the same contrast bug as ErrorSummary v1: white text on light-pink soft-fill
was unreadable. Now uses surface bg + critical border + primary text + critical
strong/heading color. Same dark-mode treatment.

shared/playground-examples/tier3-preview.html (~470 lines): live demo for all
8 components with realistic Norwegian mock-data (Lier kommune ROS T-001
threat, AI Act timeline 2026-05-02 today-marker, FRIA EU Charter rights, M365
capability-matrix, 4-worker utredning grid). Used to validate visual coherence
before committing.

Updates shared/playground-design-system/README.md with Tier 3 component table
and provenance note distinguishing v0.1 (claude.ai/design) from this addition
(Claude Code).

Remaining for v0.2: 12 plugin-specific Tier 3 components (sankey/toxic-flow,
fleet-overview, kanban Keep/Review/Remove, maturity-ladder, classify-and-
transform, cycle-ribbon, persistent-antipattern badge, suppressed-signals,
ExpansionCard, ReadMore, FormProgress, Aspirational vs Committed visual). To
be generated by claude.ai/design in a supplement session before plugin
Playground work begins.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

shared/playground-design-system/base.css

@@ -170,9 +170,12 @@ button { font-family: inherit; }
 .inline-message--info     { border-color: var(--color-state-info);    background: #EAF3FB; color: #08416B; }
 .inline-message--success  { border-color: var(--color-state-success); background: var(--color-severity-low-soft); color: var(--color-severity-low-on); }
 .inline-message--warning  { border-color: var(--color-state-warning); background: var(--color-severity-medium-soft); color: var(--color-severity-medium-on); }
-.inline-message--error    { border-color: var(--color-severity-critical); background: var(--color-severity-critical-soft); color: var(--color-severity-critical-on); }
+.inline-message--error    { border-color: var(--color-severity-critical); background: var(--color-surface); color: var(--color-text-primary); }
+.inline-message--error strong, .inline-message--error b { color: var(--color-severity-critical); }
 
-[data-theme="dark"] .inline-message--info { background: #0E2A3F; color: #9CC0EA; }
+[data-theme="dark"] .inline-message--info  { background: #0E2A3F; color: #9CC0EA; }
+[data-theme="dark"] .inline-message--error { background: var(--color-surface); color: var(--color-text-primary); }
+[data-theme="dark"] .inline-message--error strong, [data-theme="dark"] .inline-message--error b { color: #F09095; }
 
 /* ---------- Form controls ---------- */
 .input, .select, .textarea {