feat: add signal resource agent proof

[blove]

Summary

• add a private signal-resource-to-Agent adapter proof under chat
• cover Agent conformance, message/tool-call projection, status/error mapping, and submit/stop/retry/regenerate delegation
• update the M6 plan checklist with the private-boundary decision and verification evidence
• harden chat e2e browser hygiene for aborted icon-font loads observed in CI

Verification

• NX_DAEMON=false npx nx test chat --skip-nx-cache --outputStyle=static --testFile=src/lib/agent/signal-chat-resource-agent.spec.ts
• NX_DAEMON=false npx nx test chat --skip-nx-cache --outputStyle=static
• NX_DAEMON=false npx nx test ag-ui --skip-nx-cache --outputStyle=static
• NX_DAEMON=false npx nx test langgraph --skip-nx-cache --outputStyle=static
• NX_DAEMON=false npx nx lint chat --skip-nx-cache --outputStyle=static
• NX_DAEMON=false npx nx build chat --skip-nx-cache --outputStyle=static
• NX_DAEMON=false npx nx e2e examples-chat-angular --skip-nx-cache --outputStyle=static -- --grep "streaming markdown table|streaming code fence"
• NX_DAEMON=false npx nx lint examples-chat-angular --skip-nx-cache --outputStyle=static
• git diff --cached --check
• staged forbidden-reference scan excluding docs/superpowers/**

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Project	Deployment	Actions	Updated (UTC)
threadplane	Ready	Preview, Comment	Jul 8, 2026 11:53pm

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Automated approval: this PR received an intelligent (AI) code review. See the review comments on this PR.

[github-actions]

Claude finished @blove's task in 0s —— View job

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[github-actions]

Claude finished @blove's task in 0s —— View job

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I'll analyze this and get back to you.