feat: add patch-style draft updates for agents

[forestileao]

Summary

• add patch_draft to superplane_app so agents can send small graph operations instead of full canvas_yaml
• apply patches through the internal canvas changeset patcher, validate against existing rules, and stage canonical canvas YAML
• default patch_draft auto-layouts affected connected components, with explicit auto_layout overrides for full canvas or custom seeds
• update agent tool schema, access reporting, and prompts to prefer patch updates for large apps

Closes #5726

Validation

• make test PKG_TEST_PACKAGES=./pkg/agents/...
• make format.go
• make lint && make check.build.app

[superplanehq-integration]

👋 Commands for maintainers:

• /sp start - Start an ephemeral machine (takes ~30s)
• /sp stop - Stop a running machine (auto-executed on pr close)

[superplane-gh-integration-9000]

Risk: 45/100 (medium)

Summary

Replaces the full-YAML update_draft agent action with a structured patch_draft action that accepts ordered graph operations (add/update/delete nodes and edges), applies them through the internal canvas changeset patcher, and defaults auto-layout to affected connected components.

Concerns

• patchChangeNode does not validate node id is non-empty after the NodeID fallback — empty ID passed silently to patcher.
• patchChangeEdge does not validate source_id or target_id are non-empty before building the edge.
• update_node schema exposes component and integration_id fields that are silently ignored by the implementation.
• Hard rename update_draft → patch_draft with no backward-compat shim breaks in-flight agent sessions at deploy time.
• normalizePatchOp aliases (replace_node, remove_node, remove_edge) are untested.
• customToolResultsLogFields logic is duplicated between anthropic/provider.go and agent_stream_worker.go.

Recommended reviewers: lucaspin, re-pixel

[cursor]

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[forestileao]

👍