chore: drop bunfig keys Bun ignores and fix broken npm scripts

[navbytes]

Cleanup of tooling config that does not do what it says.

bunfig.toml — keys Bun silently ignores

Bun does not warn about unknown bunfig keys, so these had read as working configuration for a long time. Each removal was verified, not assumed:

Removed	How it was checked
[build] (whole section)	Set minify/sourcemap, ran bun build with no CLI flags → no .js.map, output kept original identifiers. Not a bunfig section at all.
[test] timeout = 5000	Set timeout = 100, ran a 300ms test → passed.
[test] bail = false	Set bail = true with a failing first file → second file still ran.
[install] frozen	Docs: the real key is frozenLockfile.
[install] auto = true	Real key, but takes "auto"|"force"|"disable"|"fallback" — not a boolean. It also governs runtime auto-install of missing packages, not "peer dependencies" as the comment claimed.
[install] parallel	No such option.
[install.scopes]	Both scopes pointed at the default registry — a no-op.

registry is kept despite matching the default: stating it explicitly stops a user-level .npmrc or bunfig from silently redirecting installs for this project.

The file header now records what was removed and why, so the same keys don't get re-added.

Three npm scripts were broken

bun --shell '<command>' misuses --shell, which takes bun or system, not a command. clean, clean:all and dev:extension errored on every invocation:

error: Expected --shell to be one of 'bun' or 'system'.
Received: "rm -rf dist dev node_modules/.vite"

Confirmed pre-existing (same failure with this branch's bunfig change stashed). Scripts already run under Bun's shell via [run] shell, so the wrapper was only ever wrong. bun run clean now actually deletes its targets.

One judgement call worth reviewing

dev:extension needed more than the syntax fix. Without --mode development, Vite defaults to production, setupDevEnvironment() is never registered (it's gated on !isProduction), and output lands in dist/ — making the script identical to bun run build despite its name. With the flag it produces dev/, which is what .gitignore's dev/* expects.

No regression risk, since the script never ran at all before — but this is a behaviour choice rather than a mechanical fix, so it's the bit to push back on if you disagree.

Also dropped ./tests/example.test.ts from the four test scripts; that file doesn't exist and Bun was silently ignoring it.

Verification

• Build succeeds; 495 unit pass; svelte-check 4053 files, 0 errors; biome ci clean (2 pre-existing warnings)
• 54 e2e pass in real Chrome
• bun run clean and dev:extension confirmed working by direct execution

An earlier local e2e run on this branch showed 2 beforeAll Chrome-launch timeouts; that was machine load average 49, and the suite passes 54/54 once load dropped.