Stop a bullet's open editor taking Studio down on the next keystroke

[IanHeinrich]

What and why

Ported from IanHeinrich/CareerForge#46, where this was reported from production. cv-forge's copy of the code was character-identical, so it has the same bug.

Opening a bullet's inline text editor in Studio and then typing anything threw on every following rebuild:

RangeError (end): Invalid value: Not in inclusive range 0..8: -1

That aborts the Studio subtree mid-update — the preview goes blank and the error repeats every frame.

VaultItemSelectorList.didUpdateWidget closes an open editor when the entry it belongs to leaves the CV, and recovered that entry by splitting the editor's id on its last underscore. That holds for the two ids the widget composes itself — '<itemId>_title' and '<itemId>_<index>' — but the bullet sub-list passes a bullet's own bare id. A bullet id is a uuid, or exp-1-b1 in the worked example; neither contains an underscore, so lastIndexOf returns -1 and substring(0, -1) throws. The 8 in the message is 'exp-1-b1'.length — anyone on the example CV hits it first.

Wrong twice over: had a bullet id happened to contain an underscore, the split would have named an entry that does not exist and the editor would have silently closed itself instead.

The owner is now carried alongside the id rather than parsed back out of it (typedef _OpenEditor = ({String id, String ownerId})), since only the call site knows which entry a row hangs off — and for a bullet the id genuinely does not say. The three call sites each bind their own owner; the string surgery is gone.

The second commit is unrelated to the bug and dev-only: the Studio preview would not come up locally at all, because it rasterizes build/web/pdfjs/pdf.min.mjs and tool/serve_web.mjs's MIME table had no .mjs entry — a module script served as application/octet-stream is rejected under strict MIME checking, so the preview spins for ever with the only clue in the browser console. That blocked the browser check this template asks for. Pages already types .mjs correctly.

How it was verified

• dart format --output=none --set-exit-if-changed .
• flutter analyze — no issues found
• flutter test --exclude-tags=golden — 888 pass
• Checked in the browser (required for anything under lib/features/studio/widgets/)

The new test reproduces the production error against the pre-fix code exactly: 0..8: -1 for the fixture id and 0..36: -1 for a uuid.

Browser check, on the example CV: Studio → Work history → expand a bullet sub-list → open a bullet's inline editor → type. The editor stays open, the text takes, the count moves to "tailored", the PDF preview stays rendered, and the console carries no RangeError.

Goldens

• No golden baselines affected

Anything else

Two things from the upstream PR were deliberately left out as CareerForge-specific: the 0.0.10 → 0.0.11 version bump — cv-forge is on 2.24.0 and backup_service.dart reads packageVersion rather than a duplicated literal, so there is nothing to keep in sync — and the docs/roadmap.md entry. Say the word if a release bump is wanted here.