chore(deps): update rx4 to 0.6.3

[undivisible]

Updates rx4 from 0.5.0 to the published 0.6.3 release, retaining the existing selected feature set.

Validation: dependency resolution succeeded; full cargo check is running in the release-update workspace.

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Note

Medium Risk
rx4 owns the core agent loop via RotaryAgentBridge, so a minor version bump can introduce API or behavior changes even without local code edits.

Overview
Bumps the rx4 agent harness dependency from 0.5.0 to 0.6.3, keeping the same feature set (ipc, providers, skills, graph-memory).

No application code changes — only Cargo.toml and Cargo.lock.

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[undivisible]

Fixed the rx4 0.6.3 ToolResult initializer by explicitly preserving the prior unclassified-error behavior (error_kind: None). CI is rerunning.