feat: tell if each thrown exception was caught

[lukecotter]

📝 Overview

Tell if each thrown exception was caught. A consumer that reports what failed in a transaction needs this fact. Today it must read it off the raw events itself.

🛠️ Changes

• Add isCaught: boolean | null to the details of each EXCEPTION_THROWN event. It is the parser's reading of the row after the throw; the log does not state it.
  • A FATAL_ERROR gives false. Any other row gives true, so a finally block that logs before a FATAL_ERROR reads true.
  • Throws with only exit lines between them share one answer, so a throw that a catch block wraps and throws again is false too.
  • The log end, a limit block (CUMULATIVE_LIMIT_USAGE, LIMIT_USAGE_FOR_NS, TESTING_LIMITS, CUMULATIVE_PROFILING_BEGIN) or dropped lines give null.
• engine/throws.ts reads every decided throw in one pass, on the first read. EventLines holds the result for its log. The scan does not change.
• Fix: a max-size issue that moves to a closed frame now keeps where the dropped part starts (Issues.replace). Without it, a throw before a max-size cut read true.
• Details and Caught terms in CONTEXT.md. The README and .changeset/v1.md say what details holds.

🧩 Type of change

• 🐛 Bug fix — fixes an issue
• ✨ Feature — adds new functionality
• ♻️ Refactor — no behaviour change
• ⚡ Performance
• 📝 Docs
• 🔧 Chore — tooling, CI, deps
• 💥 Breaking change

🔗 Related issues

Part of #123 (caught).

✅ Checklist

• Tests added/updated
• pnpm run ci passes locally
• Changeset added (pnpm changeset) if this affects the published package
• Docs updated if behaviour or the public API changed

[codspeed]

Merging this PR will not alter performance

✅ 6 untouched benchmarks

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_{Comparing feat/exception-caught (bea7ec5) with main (c564955)}