# Add an "IsError" worked example to the Parameters docs

From WISHLIST.md: add a use case to the docs showing how to create a parameter `IsError` that's `true` for any message containing "error" (case-insensitive) and `false` otherwise.

Add a worked example to the "Parameters" section in `webapp/src/components/Docs.tsx` (alongside the existing `duration` worked example) showing how to declare a boolean `IsError` param: regex `(?i)error`, kind `boolean`, no capture group needed, true/false on every line.

This use case surfaces missing functionality — today params always need a capture group and are *omitted* (not `false`) on non-matching lines, and there's no boolean kind. Ticket 018 (boolean param kind) was created to cover that missing functionality; this docs ticket depends on it landing first (so the worked example describes real, working behavior) — indicate in the doc's example that it relies on the boolean param kind.

## Acceptance criteria
- Depends on ticket 018 (boolean param kind) — implement/land that first.
- "Parameters" section in `Docs.tsx` gets a new worked example: declaring `IsError` with regex `(?i)error`, kind `boolean`, showing it as `true`/`false` on every log line.
- The existing `duration` worked example and surrounding prose are otherwise unchanged.