amyboardweb: restore DX7 patch levels; skip disabled panes on DX7

[bwhitman]

Summary

• Drop trailing ,,0,0 from OSCA/OSCB level change_code in amy_parameters.js so the a (amp) command no longer clobbers EG0/LFO coefs — mostly-restores DX7 patch sound.
• Disable the Osc A pane (in addition to Osc B + ADSR) for DX7 presets across all three load paths: the editor preset loader (editor/index.html), spss.js patch loader (load_saved_patch_file_into_current_channel), and apply_zd_dump_to_knobs (Pull).
• Stop blasting initial knob-CC updates for disabled panes on DX7 preset load:
  • send_all_knob_cc_mappings (spss.js) skips knobs whose section is in window._disabled_sections.
  • refresh_knobs_for_channel (amy_parameters.js) skips the onKnobCcChange loop for those knobs.
  • The editor preset loader now marks Osc A / Osc B / ADSR disabled before calling send_all_knob_cc_mappings, so the skip takes effect on first load.

Deployed to https://amyboard-wip.vercel.app for collaborator testing.

Test plan

• Load a DX7 preset: Osc A, Osc B, ADSR panes are all visibly disabled.
• Load a DX7 preset: no ic… wire commands go out to AMY for Osc A / Osc B / ADSR knobs on initial load.
• DX7 patches actually make sound (the ,,0,0 removal should restore amp).
• Load a non-DX7 (AMYboard/Juno) preset: all panes remain enabled and knob CC mappings send normally.
• Pull in control mode applies the same disable + skip behavior via apply_zd_dump_to_knobs.

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