chore: capitalize first letter of remaining subdirectory names

chore: capitalize first letter of remaining subdirectory names

The earlier `chore: capitalize first letter of project directory names`

(ea54189) commit only renamed top-level project directories.

17 second-level subdirectories across 3 projects were left with

lowercase first letters — a leftover that violated the same rule.

Directories renamed (17):

  Cases/Roll/

    roll 27mm              -> Roll 27mm

    roll 55mm              -> Roll 55mm

    roll for welding wire  -> Roll for welding wire

  Miscellaneous/12V Lead-Acid battery changer and terminal/

    body and covers                              -> Body and covers

    connector terminal                           -> Connector terminal

    current limiter                              -> Current limiter

    indicator panel                              -> Indicator panel

    main board                                   -> Main board

    transformer and AC DC converter board        -> Transformer and AC DC converter board

  Miscellaneous/USB desk fan mod/

    schematic                 -> Schematic

  Miscellaneous/Portable stereo active speaker/

    battery holder            -> Battery holder

    center box                -> Center box

    extra capacitors          -> Extra capacitors

    front panel               -> Front panel

    main board                -> Main board

    mono audio amp module     -> Mono audio amp module

    speakers                  -> Speakers

Org link references in the affected project index.org files were

updated to match the new directory names. File names inside the

renamed directories (which often contain the lowercase word as

part of a descriptive label, e.g. `main board, 1.png`) are

content and were intentionally not renamed.

One pre-existing violation remains out of scope for this commit:

`Optics/35mm film copying device` — its first letter is lowercase

after the leading digit, but the first *character* is a digit so

it was not matched by the same rule used here.