Rework the single Effect return into a drained effect queue
(Save{path,scope,contents} / Load / Publish / Pull) so one action can
ask the host for several ordered steps: opening a non-resident file
queues a Save of the outgoing dirty buffer then a Load of the target.
Keep the active buffer's fields inline on Editor and park inactive
buffers in a small LRU (<=3 resident = active + 2); switching back to a
resident buffer restores its caret/scroll/undo without touching the SD.
A dirty parked buffer is saved before eviction, so nothing leaves RAM
unsaved. `:e <path>` opens by prefix (/sd/repo -> Tracked, /sd/local ->
Local); `:sync` is refused in-core for a Local buffer.
Firmware drains the queue to empty each batch (a Load can cascade an
eviction Save) and persistence generalises the atomic save off the
hard-coded notes.md into load_path/save_path.
Also bump the side panel to FONT_9X15 and the `:` command line to
FONT_10X20 for legibility, word-wrapping the snackbar so a long notice
keeps its actionable tail.
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