fix(search): --ai no longer hangs — parseArgs missing index increment

[edwinhu]

Problem

superhuman search "<query>" --ai (Superhuman's server-side AI search — the only search path that reaches archived / "done" mail) silently produced zero output and hung. Repro:

superhuman search "pebble pre-order confirmation" --account eddyhu@gmail.com --ai --json
# → no output, never returns

Root cause

In parseArgs, the --ai flag's switch case set options.ai = true but never advanced the parser index i, while every sibling boolean flag does (--json, --focused, --include-done, …). Because parseArgs increments i manually per-flag inside while (i < args.length), the missing increment pinned i on the --ai token and spun an infinite loop. The CLI never even reached cmdSearch — it hung with no output on every --ai invocation.

Broken since v0.25.0 (778a6de, 2026-04-07). The existing ai-search.test.ts only exercised askAISearch() directly, never the CLI argument parser, so the regression went unnoticed.

The backend endpoint (v3/ai.askAIProxy) was never the problem — direct probing showed it returns HTTP 200 with full results (retrievals + AI summary) in ~10–30s. The prior "AI search is deauthorized" hypothesis was a red herring.

Fix

• Add the missing i += 1 to the --ai case.
• Add a forward-progress backstop to the parse loop: capture i before dispatch and throw a clear error if it did not advance. Any future missing-increment regression now fails loudly and actionably instead of hanging silently.
• Export parseArgs and add src/__tests__/parse-args.test.ts: covers --ai (both --ai and --ai=… forms, every position relative to other flags) plus a forward-progress sweep over all boolean flags — each under a 5s timeout so a reintroduced hang fails the test instead of stalling the suite.

Verification

• search "pebble pre-order confirmation" --account eddyhu@gmail.com --ai --json → exit 0, 1212 bytes (2 retrievals + ai_summary). Non-JSON path also renders the AI narrative + thread IDs.
• Full suite: 524 pass, 0 fail (bun test).

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