Add per-tool suppression for unknown tool name notifications (#560)

[rajbos]

Closes #560

Summary

Users can now suppress individual tool names from the Unknown Tools Found section in the Usage Analysis dashboard. This is useful when testing a new MCP server that doesn't yet have a friendly display name, without losing visibility into other unrecognised tools.

Changes

vscode-extension/package.json

• Added new setting copilotTokenTracker.suppressedUnknownTools (array of strings, default []) with a clear description.

vscode-extension/src/extension.ts

• getUsageAnalysisHtml() — reads suppressedUnknownTools from VS Code settings and injects it into __INITIAL_USAGE__.
• Message handler in showUsageAnalysis() — handles the new suppressUnknownTool webview message: appends the tool name to the setting (global scope) and refreshes the panel.

vscode-extension/src/webview/usage/main.ts

• UsageAnalysisStats — extended with optional suppressedUnknownTools?: string[].
• getUnknownMcpTools() — filters out suppressed tool names before returning the list.
• Unknown tool chip — each chip now renders a 🔇 button (data-suppress-tool attribute); event delegation in bootstrap() posts suppressUnknownTool to the extension host.

How it works

1. User sees an unknown tool name in the Unknown Tools Found section.
2. They click the 🔇 button next to that tool.
3. The extension adds the tool name to copilotTokenTracker.suppressedUnknownTools in VS Code global settings and refreshes the dashboard.
4. The tool no longer appears in the section; all other unrecognised tools remain visible.
5. Users can remove a name from the setting at any time via VS Code Settings to make it reappear.