v2.0.0 dedup logic discards real token data when proxy writes two records per message (tokens=0 placeholder + real values) #18

Title: v2.0.0 dedup logic discards real token data when proxy writes two records per message (tokens=0 placeholder + real values)

Body:

Bug Description

v2.0.0 introduced deduplication via createUniqueHash() (messageId + requestId). When using a proxy (e.g. mimo, ccswitch) that writes two records per message to the .jsonl files — a placeholder with tokens=0 first, then a second record with real token counts — the dedup keeps the zero-value record and discards the real one.

This causes the status bar and webview to show drastically incorrect usage (e.g. \$0.20 instead of \$7.98 for today).

Root Cause

Proxies like mimo write records to jsonl in a streaming fashion:

// Record 1 — written immediately when streaming starts (placeholder)
{"message":{"id":"msg_xxx","usage":{"input_tokens":0,"output_tokens":0}}, "timestamp":"2026-06-01T03:43:44.657Z"}
// Record 2 — written after response completes (real values)

{"message":{"id":"msg_xxx","usage":{"input_tokens":271,"output_tokens":5774}}, "timestamp":"2026-06-01T03:43:46.182Z"}

Both records share the same messageId (and both have no requestId), so createUniqueHash() generates the same hash for both. The dedup in loadUsageRecords() keeps the first occurrence and skips the rest:

// dataLoader.js line ~320

const uniqueHash = this.createUniqueHash(data);

if (uniqueHash && processedHashes.has(uniqueHash)) {

continue;  // ← skips the real-value record

}

Impact

Out of 188 unique message hashes for today, 185 had the first record with tokens=0 and the second with real values.

Suggested Fix

When a duplicate hash is encountered, compare token sums and keep the record with higher values instead of blindly skipping:

// In loadUsageRecords(), replace the simple skip with:
if (uniqueHash && processedHashes.has(uniqueHash)) {
    const newUsage = data.message.usage;
    const newSum = (newUsage.input_tokens || 0) + (newUsage.output_tokens || 0)
        + (newUsage.cache_creation_input_tokens || 0) + (newUsage.cache_read_input_tokens || 0);
    const existing = records[hashToIndex.get(uniqueHash)];
    const exUsage = existing.message.usage;
    const exSum = (exUsage.input_tokens || 0) + (exUsage.output_tokens || 0)
        + (exUsage.cache_creation_input_tokens || 0) + (exUsage.cache_read_input_tokens || 0);
    if (newSum > exSum) {
        records[hashToIndex.get(uniqueHash)] = data;
    }
    continue;
}

This also requires changing processedHashes from a Set to a Map (hash → array index).

Environment

• Extension version: 2.0.0
• Claude Code version: 2.1.159
• Proxy: mimo (ccswitch)
• OS: Linux (Manjaro, kernel 6.12)
• VS Code: Remote SSH (vscode-server)

Verification

After applying the fix locally, today's data correctly shows 233 records / $7.98 instead of 4 records / $0.20.