[Refactor] Extract webview message handling & state posting into WebviewBridge from ClineProvider.ts #26

Parent Issue

Part of #8 — Code Refactor on Monolith Files

Related upstream issues

• UI becomes unresponsive during long tasks due to inefficient state updates RooCodeInc/Roo-Code#6513 — UI becomes unresponsive after ~1000 messages due to postStateToWebview() sending the full conversation history on every update (O(n²) data transfer). Extracting this cluster into WebviewBridge is the prerequisite for switching to incremental state updates.

Summary

Extract the webview message dispatch and state posting cluster from src/core/webview/ClineProvider.ts into a dedicated WebviewBridge module, and address the O(n²) state update performance issue.

Scope

Methods to extract:

• postMessageToWebview()
• postStateToWebview() (and variants without task history / cline messages)
• getStateToPostToWebview()
• broadcastTaskHistoryUpdate()
• Code index status update logic

State owned:

• view?: vscode.WebviewView | vscode.WebviewPanel
• webviewDisposables: vscode.Disposable[]
• isViewLaunched: boolean
• codeIndexManager?
• codeIndexStatusSubscription?

Estimated size: ~600–700 lines

Performance improvement opportunity

Once extracted, WebviewBridge can be updated to send incremental diffs rather than the full conversation state on each update, resolving the O(n²) degradation described in RooCodeInc/Roo-Code#6513.

Constraints (from #8)

• Preserve message dispatch order
• Maintain event subscription teardown
• Run type checks after extraction
• One extraction per commit