Replace /post's managed filepond field with a controlled 'photos' field
(theme forms/fields/photos) + picker logic in post-form.js: magic-byte
sniff (ISO-BMFF ftyp brands, not filename/MIME), lazy import('heic-to')
only for real HEIC (deferred 3MB chunk via ESM splitting), per-thumbnail
converting/uploading/done/error states, in-flight counter gating Submit,
and fail-closed skip on conversion failure. Converted JPEGs POST to Grav's
AJAX file-upload route into the form flash (the only path copyFiles reads),
so add-page-by-form attaches them on submit. Web-format photos pass through.
Refs R8, R9, R16, R17, AE1, AE4, KTD4.
Add a page-scoped js/src/post-form.js bundle (built ESM + code-splitting
so U4's heic-to becomes a deferred chunk) loaded only by post-form.html.twig
via a new base head_assets block. EasyMDE replaces the bare textarea with a
minimal toolbar (bold/italic/list/link/preview), FA-free via CSS glyphs, and
syncs codemirror.save() on change + capture-phase submit so the inline
required-field validator and payload see the live value.
Refs R7, R15, KTD2, KTD3.
m038
