AO3-7130 Hide non-interactive submit terms in tag work filters

[noahbravo]

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Issue

https://otwarchive.atlassian.net/browse/AO3-7130

Purpose

Fixes a screen reader issue on the tag works filter page where a visually hidden non-interactive submit landmark (<dt class="landmark">Submit</dt>) was still exposed to assistive technologies.

Changes made:

• Added aria-hidden="true" to the two submit landmark <dt> elements in app/views/works/_filters.html.erb.
• Replaced ts("Submit") with t(".submit_landmark") for those two lines to satisfy i18n lint.
• Added en.works.filters.submit_landmark in config/locales/views/en.yml and normalized locale file order (no behavior change).
• Kept existing structure and styling unchanged (minimal, low-risk fix scoped to the reported page).

I noticed that this pattern appears in other parts of the codebase as well, but limited this change to the reported page to keep the fix minimal and low-risk.

Testing Instructions

Follow the reproduction steps in AO3-7130:
https://otwarchive.atlassian.net/browse/AO3-7130

Expected behavior:

• NVDA / TalkBack should no longer announce a stray non-interactive “Submit” term in the filter area.
• The actual “Sort and Filter” submit buttons should remain announced and operable.
• Visual layout should remain unchanged.

Automated tests:

• No new automated tests were added for this change.
• Existing automated checks required an i18n key and locale normalization update, both included in this PR.
  This issue affects screen reader behavior on hidden semantic elements and was validated with manual accessibility testing.
• This issue affects screen reader behavior on hidden semantic elements and was validated with manual accessibility testing.

Screenshots

Before:

After:

Credit

Name: Noah Bravo
Pronouns: they/them

[sarken]

The landmark class is for text intended to be invisible to sighted users but read by screen readers, so we should avoid using aria-hidden="true" in combination with it -- they're at cross purposes with each other. For things we want to hide from both screen readers and sighted users, we should use the hidden class.

[noahbravo]

Thanks for the clarification. I've updated this to use the hidden class instead of combining landmark with aria-hidden="true", so it follows the intended pattern.
I noticed similar instances in other templates as well, but kept this PR scoped to AO3-7130.