Fix PFL/LINE TO MASTER control counts and document quantize default

- CUE DECK A/B/C/D was wrong: there are only 2 physical PFL buttons
  (one per channel strip), which auto-switch between A/C and B/D as the
  deck assigned to that strip changes.
- LINE TO MASTER is two analog controls (PAN and LEVEL), not one.
- Document the new Quantize on by default mapping setting.

Author: dtavan

source/hardware/controllers/denon_mc3000.md

@@ -61,9 +61,10 @@ inputs only - not available to Mixxx as audio devices.
 
 :::{note}
 {hwlabel}`MASTER LEVEL`, {hwlabel}`MIC LEVEL`, {hwlabel}`MONITOR PAN`,
-{hwlabel}`MONITOR PHONES`, and {hwlabel}`LINE TO MASTER` are fully analog
-on this hardware and are not sent over MIDI at all, so adjusting them
-changes nothing on screen in Mixxx.
+{hwlabel}`MONITOR PHONES`, and the {hwlabel}`LINE TO MASTER` {hwlabel}`PAN`
+and {hwlabel}`LEVEL` knobs are fully analog on this hardware and are not
+sent over MIDI at all, so adjusting them changes nothing on screen in
+Mixxx.
 :::
 ## Mapping Settings
 
@@ -83,6 +84,9 @@ controller and the Denon MC3000 mapping:
   enabled by default at startup, for all four decks (default: off).
 - **KEY LOCK on by default** sets whether {hwlabel}`KEY LOCK` is
   enabled by default at startup, for all four decks (default: off).
+- **Quantize on by default** sets whether quantize
+  ({hwlabel}`SHIFT` + {hwlabel}`SYNC`) is enabled by default at startup,
+  for all four decks (default: off).
 
 ## Mixer Section
 
@@ -93,10 +97,10 @@ controller and the Denon MC3000 mapping:
 | {hwlabel}`LEVEL` | Channel pregain/trim. |
 | {hwlabel}`FILTER` | QuickEffect filter. |
 | {hwlabel}`HI` / {hwlabel}`MID` / {hwlabel}`LOW` | 3-band channel EQ. |
-| {hwlabel}`CUE DECK A` / {hwlabel}`CUE DECK B` / {hwlabel}`CUE DECK C` / {hwlabel}`CUE DECK D` | Headphone cue (PFL) toggle, one button per deck letter. |
+| {hwlabel}`CUE DECK A/C` / {hwlabel}`CUE DECK B/D` | Headphone cue (PFL) toggle. Only 2 physical buttons, one per channel strip; each toggles PFL for whichever deck (A or C on the left strip, B or D on the right strip) is currently active on that strip. |
 | {hwlabel}`KEY LOCK` | Toggles keylock for the deck. Off by default at startup for all four decks; see Mapping Settings above to change the default. |
 | {hwlabel}`SYNC` | Beat-syncs the deck. Hold past a short delay to enable continuous sync lock instead of a one-time sync. The LED lights while sync is active. |
-| {hwlabel}`SHIFT` + {hwlabel}`SYNC` | Toggles quantize for the deck. |
+| {hwlabel}`SHIFT` + {hwlabel}`SYNC` | Toggles quantize for the deck. Off by default at startup for all four decks; see Mapping Settings above to change the default. |
 
 :::{hint}
 {hwlabel}`LEVEL`, {hwlabel}`FILTER`, {hwlabel}`HI`, {hwlabel}`MID`,
@@ -197,5 +201,6 @@ playing.
   crossfader between audio and video assignment, has no Mixxx equivalent.
 - {hwlabel}`DUCKING` is not mapped to anything.
 - {hwlabel}`MASTER LEVEL`, {hwlabel}`MIC LEVEL`, {hwlabel}`MONITOR PAN`,
-  {hwlabel}`MONITOR PHONES`, and {hwlabel}`LINE TO MASTER` are fully analog
-  hardware controls, invisible to MIDI.
+  {hwlabel}`MONITOR PHONES`, and the {hwlabel}`LINE TO MASTER` {hwlabel}`PAN`
+  and {hwlabel}`LEVEL` knobs are fully analog hardware controls, invisible
+  to MIDI.