Remove Copilot extension check and startup wait

[Copilot]

The extension unnecessarily delayed startup (2–5s) when Copilot extensions were installed but not yet active, blocking users who rely solely on OpenCode or other non-Copilot tools.

Changes

• scheduleInitialUpdate() — replaced the three-branch Copilot detection logic with a single unconditional 100ms startup delay; analysis begins immediately regardless of Copilot extension presence or state
• Removed recheckCopilotExtensionsAfterDelay() — only served the delayed-start path
• Removed initialDelayTimeout property and its disposal cleanup — no longer needed

// Before: branched on Copilot extension state, waited up to 5s
private scheduleInitialUpdate(): void {
    const copilotExtension = vscode.extensions.getExtension('GitHub.copilot');
    // ... 3-way branch with 2–5s delay if extensions exist but inactive
}

// After: always starts immediately
private scheduleInitialUpdate(): void {
    this.log('🚀 Starting token usage analysis...');
    setTimeout(async () => { await this.updateTokenStats(); ... }, 100);
}

The informational checkCopilotExtension() log call in the constructor is unchanged.