matchAboutBlank doesn't work in dev mode

Describe the bug

setup a content script with

	matches: ["<all_urls>"],
	allFrames: true,
	matchAboutBlank: true,

build using wxt (aka npm run dev)

Go to a page with an iframe like https://www.w3schools.com/tags/tryit.asp?filename=tryhtml_iframe

Use DevTools and notice no content script is injected in the iframe

Reproduction

follow the steps above

Steps to reproduce

No response

System Info

System:
    OS: macOS 15.6.1
    CPU: (16) arm64 Apple M4 Max
    Memory: 21.73 GB / 128.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 24.5.0 - /opt/homebrew/bin/node
    Yarn: 1.22.22 - /opt/homebrew/bin/yarn
    npm: 11.6.1 - /opt/homebrew/bin/npm
    pnpm: 10.18.0 - /opt/homebrew/bin/pnpm
    Deno: 2.5.2 - /opt/homebrew/bin/deno
  Browsers:
    Chrome: 140.0.7339.214
    Firefox: 143.0.4
    Safari: 18.6
  npmPackages:
    wxt: 0.20.11 => 0.20.11

Used Package Manager

pnpm

Validations

• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.

Start by reproducing the issue with npm run dev using the shown content-script settings and the linked iframe page. Trace WXT's dev-mode content-script generation and injection path, then verify that matchAboutBlank injects the script into the iframe while preserving the existing behavior.