Gear icon dodge follows the page number's real position (BL-14901)

[andrew-polk]

Follow-up to #8182 (the landscape Picture-on-Right fix): the tester found the gear icon (format cog) still displaced away from the margin on portrait ebook pages, and the same pointless dodge occurred whenever the Book Settings "Page Numbers" control moved the number away from the bottom left.

Two commits:

1. Zero Margin portrait fix. That theme only places its page number at the bottom left on landscape pages; on portrait pages the number is centered (the device-size default), yet its 20px dodge applied everywhere. The dodge is now scoped to landscape. Also gave the default theme's dodge a unit (0 → 0px): the unitless zero made the cog's margin-left: calc(3px + var(...)) invalid, so in every default-theme book the cog sat at 0 instead of the intended 3px (harmless but wrong since ~6.0).

2. The dodge now honors the Page Numbers setting. editMode.less folds everything that determines where the number actually sits into one effective dodge, reading the same margin-override variables the appearance system writes for that setting (via container style queries): Center or Right ⇒ nothing to dodge, whatever the theme wanted; Left ⇒ the theme's full dodge even on pages whose theme moved the number elsewhere (e.g. pictureOnRight); Automatic ⇒ the theme's per-page decision, as before. Both ebook themes publish the new --formatButton-pageNumber-dodge-when-forced-left; the EFL migration books' baked-in stylesheets fall back to their ordinary dodge.

Verified live in Bloom with a 12-case matrix (both ebook themes × both orientations × all four Page Numbers settings, measuring the cog's computed margin on a Picture-on-Right page and a text-bottom control page): every case the tester reported now puts the cog at the margin, and every case where the number genuinely sits bottom-left still dodges, including landscape regression checks.

Ref: https://issues.bloomlibrary.org/youtrack/issue/BL-14901

🤖 Generated with Claude Code

Devin review

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This change is 

[andrew-polk]

[Claude Fable 5 during preflight] Consulted Devin on 2026-08-12 up to commit aa7c5bc. Review: 0 bugs, 1 Investigate flag, 3 Informational observations. The Investigate flag (default-theme books get no dodge when Page Numbers is forced Left) was posted as an inline thread, assessed as not-an-issue (the default theme reserves space so its page number sits below the text area in every case), and resolved: #8198 (comment). The informational notes (cascade verification, the 0px unit fix affecting all default-theme books by restoring the intended 3px, and the forced-left variable being published on portrait pages) all describe intended behavior. CI green at time of writing.