chore: Include Wizard header in step context

[connorlanigan]

Description

Before this PR, the header area of the Wizard component was not included in the step context. This meant that when an info link inside the header was clicked, the resulting helpPanelInteracted event did not contain information about the current step.

This PR moves the step context so that it contains the whole content area of the Wizard (i.e. without the navigation on the side).

Related links, issue #, if available: n/a

How has this been tested?

Tested manually in dev page by inspecting the generated event

Review checklist

The following items are to be evaluated by the author(s) and the reviewer(s).

Correctness

• Changes include appropriate documentation updates.
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md.
• Changes do not include unsupported browser features, see CONTRIBUTING.md.
• Changes were manually tested for accessibility, see accessibility guidelines.

Security

• If the code handles URLs: all URLs are validated through the checkSafeUrl function.

Testing

• Changes are covered with new/existing unit tests?
• Changes are covered with new/existing integration tests?

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[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: -0.02% ⚠️

Comparison is base (ea832bb) 93.48% compared to head (9bdd99a) 93.47%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1368      +/-   ##
==========================================
- Coverage   93.48%   93.47%   -0.02%     
==========================================
  Files         624      623       -1     
  Lines       16801    16770      -31     
  Branches     5552     5546       -6     
==========================================
- Hits        15707    15676      -31     
  Misses       1021     1021              
  Partials       73       73              

Files Changed	Coverage Δ
src/wizard/wizard-form.tsx	100.00% <100.00%> (ø)

... and 4 files with indirect coverage changes

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