fix: support array inputs and fixed-string entryFileNames

[EvilFaeton]

I'm not super familiar with the rolldown plugin internals, so I used Claude Code to help trace issue back through plugin hooks, understand fake-js architecture, and validate that my fix was correct and backward-compatible (hopefully).

So, I'm checking those boxes:

• This PR contains AI-generated code, but I have carefully reviewed it myself. Otherwise, my PR may be closed.
• I understand that my PR is more likely to be rejected or requested for changes if it contains AI-generated code that I do not fully understand.

Description

Hey! I ran into this while migrating monorepo from vite-plugin-dts + @microsoft/api-extractor to rolldown-plugin-dts. After building some packages with Vite 8 in lib mode output .mts files had raw fakejs arrays like [1, () => [...]] instead of actual TypeScript declarations. Downstream packages could not type-check at all.

What was happening

I'm not super familiar with the rolldown plugin internals, so it took some digging. I added debug logging to hooks and traced it down to two possible separate "bugs" (once again, I was fixing problem I've faced, not sure if it's generic and it makes sense to push it as fix) that combine together in Vite 8 lib mode:

Array inputs not handled in buildStart

Vite 8 passes options.input as array (['src/index.ts']) but buildStart only handled object inputs ({ index: 'src/index.ts' }). When input is array, inputAliasMap stayed empty so emitted DTS chunks got name: undefined instead of smth like index.d.

Fixed-string entryFileNames missing .d in output

Vite 8 lib mode provides entryFileNames as function returning fixed string (like 'index.mjs') not a template with [name]. The entryFileNames hook converted .mjs to .mts but never inserted .d, producing index.mts instead of index.d.mts. Then renderChunk did not recognize it as a DTS file and skipped the fake-js reversal.

fix

• Added else branch in buildStart to populate inputAliasMap for array inputs deriving chunk names from file basenames
• Added filename_js_to_dts() step in entryFileNames hook — same pattern that fake-js plugin already uses in its chunkFileNames hook

All 201 tests pass (195 existing + 6 new ones covering these cases).

Linked Issues

Additional context