fix: stop --pricing from being mistaken for the usage file

[ZhenghuaBao]

The bug

usage-summary.mjs picked its input file with a separate scan for "the first argv entry that does not start with --":

const file = argv.find((a) => !a.startsWith("--"));

A flag's value is not a positional argument, though. --pricing takes a path, and a path does not start with --, so putting the flag first made the price list get read as the metering file.

Why it mattered

The failure was silent rather than loud. A price list is itself valid JSON, so it parsed as a single metering row with no token fields:

node usage-summary.mjs --pricing pricing.json usage.jsonl --json
  -> calls: 1, prompt_tokens: 0

Exit 0, no warning, not even a malformed-line count — and the real usage file never read. For a script whose entire purpose is comparing model costs, a plausible-looking $0.00 is the worst possible output: it doesn't look like an error, it looks like a cheap model.

Scope

Not reachable from action.yml, which calls node "$USAGE_SUMMARY" "$USAGE_FILE" — file first, and no --pricing at all. This only bit manual cost-comparison runs, which is exactly when --pricing gets used.

The fix

Fold the two scans into one pass that advances past a flag's value. The value is only consumed when it actually is one, so a trailing --pricing or one followed by another flag does not swallow it.

Tests

6 added (27 -> 33 in this file):

• --pricing before the usage file no longer steals it, and the price list is still applied
• both argument orders produce identical output
• the first positional wins; a stray extra one does not override it
• --json is recognized wherever it appears
• a valueless --pricing does not swallow the flag after it
• a trailing --pricing with nothing after it is harmless

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