Bug: Footer.of_children omits width=100% on its outer table (#20)

[makerprism-bot]

Fixes #20.

Automated implementation for issue #20 (#20).

Produced by automation run 34e0e9af-f5c3-45a6-b1f4-58168e0107c2 using Claude Code on makerprism/typemail.

Agent's summary (last lines of output):

Implementation complete. I've successfully fixed issue #20 by adding `width="100%"` to the Footer component's outer table element.

**Changes made:**
- `lib/footer.ml`: Added `"width", "100%"` to the table attributes list (line 43)
- `test/structure_tests.ml`: Added assertions to verify `width="100%"` is present on both `Footer.v` and `Footer.of_children` paths
- `test/golden/footer.html`: Updated the expected output to include `width="100%"` in both test cases

The Footer component now matches the behavior of Section, Callout, and Spacer components, ensuring the footer table spans the full width and aligns correctly in Outlook and other email clients.

Review carefully; this is a first-attempt automated change.

[sabine]

⚠️ CRITICAL: This PR has the wrong diff

Expected (from PR title and issue #20)

This PR should fix: "Footer.of_children omits width=100% on its outer table"

Expected changes:

• File: lib/footer.ml
• Add "width", "100%" to Footer outer table attributes
• Update structure tests to assert width="100%" on footer

Actual (from PR diff)

This PR actually changes:

• File: lib/render.ml and lib/render.mli
• Adds body_background parameter to render_email
• Has nothing to do with Footer at all

What happened?

This looks like a bot automation error - the diff from PR #21 (body_background feature) got applied to PR #22 (Footer width bug).

Action needed

Please revert this branch and apply the correct diff from issue #20:

(* lib/footer.ml - add width attribute to table *)
let of_children children =
  [...]
  make @@ builder
    ~tag:"table"
    ~attributes:[
      "border", "0";
      "cellpadding", "0";
      "cellspacing", "0";
      "role", "presentation";
      "width", "100%";  (* <-- Add this *)
    ]
    ~children:[...]

Reference issue #20 for the full requirements.