* docs(readme): animate pool + combo blocks as SMIL SVG diagrams
Replace the two remaining ASCII blocks in the README with hand-authored
animated SVGs (16s loops, SMIL only — play inside GitHub's <img> sandbox,
DESIGN_SYSTEM.md palette), following the tier-cascade.svg pattern:
- pool-fair-share.svg — key pool "team-codex" fair-share quota: weights
50/30/20, generous mode lending idle shares, 50% threshold crossing,
strict mode holding each key to its cap (verbatim README copy).
- combo-always-on.svg — combo "always-on" priority strategy: 4 fallback
layers with coral hand-off on failure and an uptime bar that never
drops (zero downtime).
Both blocks keep their full flow text in the img alt. Registered in
docs/diagrams/README.md (hand-authored table).
* docs(changelog): add fragment for #7626 (pool + combo SVG diagrams)
