[Bug] Workspace browser shows default workspace files instead of agent-specific workspace

Summary

When chatting with a non-default agent (e.g., "laoA" with workspace ~/.openclaw/workspace-laoa), the ArtifactPanel workspace browser displays files from the default workspace (~/.openclaw/workspace) instead of the agent's own workspace.

This means agent-specific configurations (custom TOOLS.md entries, AGENTS.md personality configs) are not visible in the file browser, showing generic template content instead.

Steps to Reproduce

1. Create a non-default agent with a dedicated workspace (e.g., agent "laoA" → ~/.openclaw/workspace-laoa)
2. Add custom content to the agent's TOOLS.md (e.g., custom tool configs)
3. Start a conversation with that agent
4. Open the ArtifactPanel workspace browser (right panel → Workspace tab)
5. Select TOOLS.md in the file tree

Expected Behavior

• The workspace browser shows files from ~/.openclaw/workspace-laoa
• TOOLS.md displays the agent's custom content (e.g., Stock API configuration)
• File size reflects the agent's file (2.4 KB)

Actual Behavior

• The workspace browser shows files from ~/.openclaw/workspace (default)
• TOOLS.md displays only generic template content + ClawX injected section
• File size shows 1.8 KB (the default workspace version)
• The header still shows the agent name ("laoA") but the wrong workspace path

Root Cause

resolveEffectiveWorkspace() in Chat/index.tsx has priority: session → global → default. When no session workspace is bound and no global workspace is explicitly selected, it falls back to ~/.openclaw/workspace. This value is passed as workspacePath to ArtifactPanel → WorkspaceBrowserBody, overriding the agent?.workspace fallback (which only triggers when workspacePath is empty/null, but it's never empty — it's the default value).

Environment

• ClawX version: v0.5.2
• OS: macOS 15.3 (Apple Silicon)
• Agents: Multiple agents with dedicated workspaces configured in openclaw.json

Additional Information

Fix PR: #1210