Follow-up to #839. With `bun test --isolate` giving each file a fresh
module graph, the test/isolated/ split that existed to work around
`mock.module()` pollution (oven-sh/cli#258) is no longer needed.

## Merged into existing files

Per-feature tests moved into their natural counterparts:

- isolated/brew-upgrade.test.ts              → test/lib/upgrade.test.ts
- isolated/log-view-prompt.test.ts           → test/commands/log/view.test.ts
- isolated/login-reauth.test.ts              → test/commands/auth/login.test.ts
- isolated/project-delete-confirm.test.ts    → test/commands/project/delete.test.ts
- isolated/set-commits-auto.test.ts          → test/lib/api/releases.test.ts
- isolated/set-commits-auto-no-remote.test.ts → test/lib/api/releases.test.ts
                                                (merged as a single
                                                setCommitsAuto describe;
                                                getRepositoryName is now
                                                a controllable `mock()`)
- isolated/dsn/project-root.test.ts          → test/lib/dsn/project-root.test.ts

Pattern: `mock.module()` at the top of the merged file, followed by a
dynamic `await import()` for the code under test so the mocked bindings
win. The rest of the file's static imports stay as-is.

Also unblocks a previously-deferred stub in `test/lib/api/releases.test.ts`
that said "setCommitsAuto tests live in test/isolated/ because they
require mock.module() for git helpers".

## Moved as sibling files

Two isolated files tested the same subjects as existing test files but
with incompatible mocking strategies. Under `--isolate` they're safe to
keep as siblings since module state doesn't leak:

- isolated/resolve-target.test.ts  → test/lib/resolve-target.mocked.test.ts
- isolated/delta-upgrade.test.ts   → test/lib/delta-upgrade.mocked.test.ts

Both existing `resolve-target.test.ts` and `delta-upgrade.test.ts` use
real DB + mocked fetch; the `.mocked.` siblings stub out every
collaborator via `mock.module()`. The two styles can coexist in the
same directory now that module graphs are per-file.

## New files (no prior counterpart)

Three isolated DSN helpers had no target file in test/lib/dsn/:

- isolated/dsn/errors.test.ts     → test/lib/dsn/errors.test.ts
- isolated/dsn/fs-utils.test.ts   → test/lib/dsn/fs-utils.test.ts
- isolated/dsn/resolver.test.ts   → test/lib/dsn/resolver.test.ts

## Removed `scopedFetchMock` helper

`test/lib/sentry-client.test.ts` previously wrapped all its fetch mocks
with `scopedFetchMock(marker, handler)` to filter out foreign fetch
calls that leaked from other test files (CI run 24835339085). Under
`bun test --isolate` each file gets a fresh `globalThis.fetch`, so
cross-file leakage is eliminated. The 6 call sites now use `mockFetch()`
directly; the helper and its `urlOf()` dependency are gone (~30 lines).

## Other cleanups

- Removed `test/isolated/` directory
- Updated `package.json` `test:unit` to drop `test/isolated` from the
  argument list (files now live under `test/lib/` and `test/commands/`)
- `test/lib/dsn/project-root.test.ts`: `noopSpan` stub now includes
  `setAttributes` (production code calls both `setAttribute` and
  `setAttributes`)
- Replaced several `() => {}` test stubs with named `noop` functions
  to satisfy `lint/suspicious/noEmptyBlockStatements` without per-line
  biome-ignore comments

## Verification

- `bun run test:unit` — 5920 pass / 0 fail across 253 files (was 260 —
  merges consolidated 12 files into 5 new + 7 existing)
- 3 consecutive stress runs clean
- `bun run typecheck`, `bun run lint`
- `bun run lint:fix` applied one formatting tweak