feat: add all 29 code semantic porcelain commands to code-demo

Expands the CLI reference section at the bottom of code-demo.html from 14 commands to all 29, grouped into 7 categories matching the MIDI demo pattern (group header with icon, label, description, and count badge):

1. Snapshot & Inventory — symbols, languages, grep, codemap 2. Symbol Identity & Hist — blame, symbol-log, lineage, detect-refactor 3. Query & Search — query, query-history, find-symbol, code-query 4. Architecture & Quality — hotspots, stable, coupling, compare, clones, coverage, api-surface 5. Impact & Dependencies — deps, impact, dead, breakage 6. Write & Transform — patch, checkout-symbol, semantic-cherry-pick 7. Infrastructure & Gates — index, invariants, check

Renderer updated to use GROUPS array + HTML-escape (esc()) for all text fields; example blocks with intentional span tags are exempt.