feat(jetbrains): render all Mermaid diagram types in chat

Extend the in-process Kotlin Mermaid engine to cover every diagram
type Type can detect, not just flowcharts and sequence diagrams:
class, state, ER, gantt, pie, user journey, quadrant, requirement,
git graph, C4 (all five headers), mindmap, timeline, sankey, XY
chart, block, packet, kanban, architecture, radar, and treemap.

Each type gets its own parser + layout file under mermaid/, sharing
a new Sheet (mark collection/normalization), Layered (deterministic
graph layout for the class/state/er/requirement/C4 family), Scopes
(composite/boundary edge re-anchoring), Axis (chart ticks), and Lex
(bracket/quote-aware tokenizing) so the per-type files stay small.

The Art model gains a Sector mark for pie wedges plus optional
tone/soft fields for categorical chart colors, and Head gains UML/ER
arrow variants (Triangle, Diamond, Crow, Bar, ...). Existing marks
keep their prior toString() output when the new fields are unset, so
flowchart/sequence snapshots are unchanged.

Unsupported types (zenuml, venn, ...) keep the existing soft
"unsupported" note over the source rather than an error.