Add fresh child conversation tool for Agent Canvas

[smolpaws]

Summary

• add a frontend-injected canvas_conversation tool that creates a fresh child conversation instead of using SDK fork()
• reuse the parent runtime context correctly (workspace.working_dir locally, sandbox_id in cloud) while requiring the parent to pass explicit handoff context
• wire the new ActionEvent through the websocket handler and cover the adapter/tool/service behavior with focused tests

Verification

• npm ci
• npm run typecheck
• npm run test -- __tests__/services/canvas-conversation.test.ts __tests__/api/agent-server-adapter.test.ts __tests__/tools/canvas-conversation-tool.test.ts

cc @enyst

This PR was created by an AI agent (OpenHands) on behalf of the user.

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[github-actions]

✅ Mock-LLM E2E Tests

44/44 passed

Commit: 516cbc4f · Workflow run · Test artifacts

Status	Test	Duration
✅	mock-llm-acp-agent.spec.ts › mock-LLM ACP agent conversation › step 1: configure ACP agent via Settings → Agent UI	13.6s
✅	mock-llm-acp-agent.spec.ts › mock-LLM ACP agent conversation › step 2: reload and verify ACP settings are persisted in UI	5.5s
✅	mock-llm-acp-agent.spec.ts › mock-LLM ACP agent conversation › step 3: start ACP conversation and verify agent reply	6.3s
✅	mock-llm-acp-agent.spec.ts › mock-LLM ACP agent conversation › step 4: resume ACP conversation from sidebar after navigating away	5.7s
✅	mock-llm-auth-modes.spec.ts › auth mode: fresh install with runtime-injected key › reaches the onboarding modal without pre-seeded localStorage	1.3s
✅	mock-llm-auth-modes.spec.ts › auth mode: non-public key rotation › recovers when localStorage has a stale session API key	5.3s
✅	mock-llm-auth-modes.spec.ts › auth mode: public gate › shows the auth screen when no key is configured	1.2s
✅	mock-llm-auth-modes.spec.ts › auth mode: public gate › rejects an incorrect key with an inline error	1.4s
✅	mock-llm-auth-modes.spec.ts › auth mode: public gate › allows access after pasting the correct key	1.4s
✅	mock-llm-auth-modes.spec.ts › auth mode: public gate › skips auth screen for returning user with valid stored key	695ms
✅	mock-llm-auth-modes.spec.ts › auth mode: public gate › re-prompts when the server rotates its key (stale localStorage)	1.4s
✅	mock-llm-automation.spec.ts › mock-LLM automation lifecycle › step 1: setup LLM profile and register automation trajectory	7.3s
✅	mock-llm-automation.spec.ts › mock-LLM automation lifecycle › step 2: create automation and dispatch run via the UI	30.3s
✅	mock-llm-automation.spec.ts › mock-LLM automation lifecycle › step 3: verify automation and run on the automations page	6.0s
✅	mock-llm-conversation.spec.ts › mock-LLM agent-server conversation › step 1: create an LLM profile pointing at the mock LLM server	6.2s
✅	mock-llm-conversation.spec.ts › mock-LLM agent-server conversation › step 2: activate the mock-llm profile and verify settings API	6.1s
✅	mock-llm-conversation.spec.ts › mock-LLM agent-server conversation › step 3: run a conversation with the mock LLM	6.5s
✅	mock-llm-conversation.spec.ts › mock-LLM agent-server conversation › step 4: resume conversation from sidebar after navigating away	5.8s
✅	mock-llm-cross-connect.spec.ts › cross-connect: frontend-only → backend-only › frontend-only connects to a separate backend-only instance	15.7s
✅	mock-llm-cross-connect.spec.ts › cross-connect: frontend-only → multiple backends › connects to two separate backends and switches between them	20.5s
✅	mock-llm-folder-workspace.spec.ts › mock-LLM folder browser → workspace → conversation › step 1: browse to a folder, add it as a workspace, and launch a conversation with the correct working_dir	7.8s
✅	mock-llm-image-upload.spec.ts › mock-LLM image upload › attaching an image embeds it as base64 in the LLM completion call	13.3s
✅	mock-llm-model-switch.spec.ts › mock-LLM /model slash command › step 1: configure LLM, create switch-target profile, register trajectory	13.0s
✅	mock-llm-model-switch.spec.ts › mock-LLM /model slash command › step 2: start conversation, switch profile via /model, verify switch	6.9s
✅	mock-llm-onboarding-happy-path.spec.ts › onboarding happy path › completes the full onboarding flow and launches a conversation	3.7s
✅	mock-llm-onboarding-regressions.spec.ts › onboarding recent regressions › keeps the modal open on backdrop click and Escape	1.5s
✅	mock-llm-onboarding-regressions.spec.ts › onboarding recent regressions › defaults the LLM setup step to OpenAI GPT-5.5	1.7s
✅	mock-llm-partial-stack.spec.ts › partial stack: --frontend-only › serves the frontend but returns 503 for backend routes	7.4s
✅	mock-llm-partial-stack.spec.ts › partial stack: --backend-only › serves backend APIs but returns 503 for the frontend root	13.1s
✅	mock-llm-partial-stack.spec.ts › partial stack: port conflict › fails with a clear error when the ingress port is occupied	109ms
✅	mock-llm-partial-stack.spec.ts › partial stack: port conflict › starts successfully on a free port after a conflict	6.0s
✅	mock-llm-preset-automation.spec.ts › preset automation → slash command conversation › automation card sends the correct slash command to a conversation	15.8s
✅	mock-llm-preset-automation.spec.ts › preset automation → slash command conversation › direct slash command from home page triggers skill activation	13.4s
✅	mock-llm-profile-management.spec.ts › active profile deletion + reconciliation › active profile is deletable and reconciliation activates another profile	8.6s
✅	mock-llm-profile-management.spec.ts › same-model profile identity › chat header shows the correct profile when two profiles share the same model	15.2s
✅	mock-llm-profile-management.spec.ts › litellm_proxy proxy base_url preservation › re-saving a litellm_proxy profile from Basic view preserves the proxy base_url	7.8s
✅	mock-llm-skills.spec.ts › skill loading: project, user, and deletion › project skill in workspace/.agents/skills/ triggers on matching keyword	13.8s
✅	mock-llm-skills.spec.ts › skill loading: project, user, and deletion › user skill in ~/.openhands/skills/ triggers on matching keyword	13.4s
✅	mock-llm-skills.spec.ts › skill loading: project, user, and deletion › deleting a user skill removes it from subsequent conversations	13.4s
✅	mock-llm-ui-regressions.spec.ts › UI regressions › scopes standalone styles to the agent-server-ui shell	1.4s
✅	mock-llm-ui-regressions.spec.ts › UI regressions › renders critic results on agent messages and finish actions	1.4s
✅	mock-llm-ui-regressions.spec.ts › UI regressions › loads older events when scrolling up	1.6s
✅	mock-llm-ui-regressions.spec.ts › UI regressions › selected workspace persists after navigating away and returning	1.9s
✅	mock-llm-ui-regressions.spec.ts › UI regressions › cleared sessionStorage yields empty workspace selection	956ms

_{Posted by the Mock-LLM E2E workflow · results are deterministic (scripted LLM responses)}