Skip dist clean in esbuild watch mode

[sharon-wang]

The esbuild config deletes dist/ and the tsbuildinfo files at startup so one-shot builds start clean. In watch mode this is a problem: the esbuild script starts at the same time as the two tsc --emitDeclarationOnly --watch processes, with no guaranteed ordering. If a tsc watcher finishes its first emit before the rmSync runs, the clean wipes out the .d.ts files it just wrote. Because tsc's watch mode only re-emits when source changes (not when outputs go missing), those declarations never come back until you touch a source file.

This change only runs the clean for one-shot builds and skips it in watch mode. It also adds tsconfig.positron.tsbuildinfo to the one-shot clean list so both declaration builds start fresh.

[wch]

Thanks for the fix! I merged in some stuff in to main here too early and this fixes some of the issues.