test: execute webpack browser bundle without live credentials (#2498)

- [x] I understand that this repository is auto-generated and my pull
request may not be merged

## Changes being requested

- Execute the existing `ts-browser-webpack` fixture's actual webpack
output in headless Chrome during the normal credential-free ecosystem
run.
- Fail immediately on bundle/module evaluation errors, block all
non-file network requests, and assert that browser credentials remain
disabled by default.
- Preserve the existing live browser suite, webpack/module
configuration, dependencies, workflows, and SDK production code.

## Verification

- `pnpm install --frozen-lockfile`
- `./scripts/test tests/ecosystem-browser-credential-security.test.ts
tests/ecosystem-cli.test.ts` (24 tests)
- `pnpm lint`
- `pnpm exec tsc --noEmit`
- `env -u OPENAI_API_KEY
PUPPETEER_EXECUTABLE_PATH=<installed-headless-chrome>
PUPPETEER_SKIP_DOWNLOAD=true pnpm tsn ecosystem-tests/cli.ts
ts-browser-webpack --verbose`
- Confirmed that an injected webpack evaluation error and an injected
outbound request each fail the real-browser regression.

## Additional context & links

Follow-up to #2494. The production direct-browser-import fix is tracked
separately in #2495 and is intentionally not included or required for
this independently passing webpack regression.