Warn before tracing incremental builds

[liurenfeng94-ops]

Fixes #21

• inspect the selected tsconfig before running a trace
• warn when incremental or composite builds are enabled
• mention the configured tsBuildInfoFile when available
• keep trace execution working even if the config check fails
• add focused coverage for the warning helper

Validation:

• pnpm vitest run test/incremental-build.test.ts
• pnpm typecheck
• pnpm exec eslint .
• pnpm build