CLI exporters omit v1.x blocks (chart/diagram/code/table)

[alpha912]

Problem

CLI renderers/exporters do not handle v1.x block types. HTML only covers table in addition to core blocks; Markdown/JSON ignore chart/diagram/code/table entirely. This causes data loss in exports.

Evidence

• omniscript-core/cli/src/renderers/html.ts: no cases for chart/diagram/code.
• omniscript-core/cli/src/renderers/markdown.ts: no chart/diagram/code/table handling.
• omniscript-core/cli/src/renderers/json.ts: no chart/diagram/code/table handling.

Expected

• Add render/export support for chart, diagram, code, and table blocks across HTML/Markdown/JSON.
• Keep outputs aligned with spec v1.2 and existing converter behavior.
• Add tests for each block type in CLI renderers.

Acceptance Criteria

• Exports include all v1.x blocks.
• Test coverage added for each new block type.
• No regressions in existing CLI tests.