test(ag-ui): harden streaming markdown conformance

[blove]

Summary

• add deterministic AG-UI streaming fixtures for tables, blockquotes, code fences, thematic breaks, and delayed chunks
• record every relevant DOM mutation and streaming heartbeat to detect transient malformed Markdown states
• verify native table ancestry, row geometry, column alignment, and lifecycle-owned completion across a 750ms inter-chunk pause

Why

The AG-UI example previously covered final Markdown output but did not exercise progressive rendering through its complete transport. That left adapter-specific regressions, including visually detached table rows and briefly exposed closing delimiters, without browser-level protection.

Validation

• NX_DAEMON=false NX_TUI=false npx nx e2e examples-ag-ui-angular --skip-nx-cache -- --grep "heading:|code fence: assistant|bullet list:|markdown checklist matrix:|streaming markdown table:|streaming code fence:|streaming thematic break:" (9 passed)
• NX_DAEMON=false NX_TUI=false npx nx test ag-ui --skip-nx-cache
• NX_DAEMON=false NX_TUI=false npx nx lint examples-ag-ui-angular --skip-nx-cache (0 errors; 28 existing warnings in untouched files)
• NX_DAEMON=false NX_TUI=false npx nx build examples-ag-ui-angular --configuration=production --skip-nx-cache
• local Chrome smoke test for progressively streamed tables and split code fences

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Project	Deployment	Actions	Updated (UTC)
threadplane	Ready	Preview, Comment	Jul 13, 2026 10:09pm

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