Adopt Muse Spark 1.3 and fix browser benchmark boundaries

[rsproule]

Summary

• use meta/muse-spark-1.3 for the production browser subagent, preserving the benchmarked reasoning: low configuration
• align browser eval stop points with the behavior under test instead of unrelated login, traveler-info, CAPTCHA, or payment prerequisites
• allow named vertical search products such as Google Flights while retaining the general search-engine restriction
• remove the consistently CAPTCHA-blocked Expedia case and clarify hotel, Yankees, Elsewhere, and Target success criteria
• follow Eve 0.52 background subagent streams so evals attach to the real browser worker after the root turn completes
• add an opt-in native PostgreSQL URL for local A/B runs when Docker port forwarding is unavailable

Full benchmark

Ran all 10 browser tasks, one repetition, no smoke suite, from the same main commit with only the worker model changed:

• meta/muse-spark-1.3: 9/10, 242s median, 437s P95, $4.04
• zai/glm-5.2: 8/10, 409s median, 875s P95, $12.07

Muse passed the corrected Google Flights, Yankees, Target, and hotel cases. Both Elsewhere attempts encountered the same Eventbrite checkout iframe error; Muse returned a bounded failure and the baseline timed out. The other baseline failure selected a hotel whose final displayed total exceeded the explicit $300 cap.

Validation

• pnpm exec vitest run --exclude "**/.claude/**" — 82 files, 716 tests passed
• focused model normalization and browser capability tests — 15 passed
• pnpm exec oxlint . --deny-warnings --ignore-pattern ".claude/**"
• formatting checks for all changed files
• pnpm build

Known integration note

AI SDK currently logs repeated warnings that non-OpenAI reasoning parts are unsupported and skipped for Muse. Browser execution and tool calling completed successfully in the benchmark, but the warning path is noisy and should be followed up separately.

The checkout contains a pre-existing untracked .claude/worktrees tree. The aggregate local pnpm check discovers that second checkout, so validation excludes it; the repository tests and production build pass.