[benjamindehli]

The names down the left of the mixer, like strike, swell and level, don't explain themselves. Someone new to the instrument had to open the manual to find out what STRIKE does, or what "level" under KEY OFF means. The controls in the bars along the top already had help text, but the row names had none.

Holding the pointer over a row name now shows a short tooltip saying what the row does. Every name in the gutter has one, the section headings and the cents and dB readouts included. The headings also say that clicking them folds the section. The two shape, rate and depth rows say whether they belong to the vibrato or the tremolo, and the mute and solo line names the right key for Option-click on each platform. The texts follow the manual's own description of each row.

The names are painted as text with no component of their own, so the gutter works out which row is under the pointer from the same layout it draws the names with. A folded row has no tooltip, and the rows below it keep theirs as they move up. Only LEVEL's caption has one, not the fader band under it. The texts sit in rowHelp in Theme.cpp, beside rowLabel.

What changes for users

• Holding the pointer over a row name in the gutter shows what that row does.
• The controls page says so, above the table of rows.

How it was checked

A new runtime test lays out the gutter as it is drawn and checks that:

• every row with a name has its own line of help, no two are the same, and a row with no name has none
• the pointer on each name gets that name's help
• with ENVELOPE folded, its heading keeps its help, no point in the gutter gives STRIKE's, and the KEY OFF rows below keep theirs
• the fader band under LEVEL's name gives no row help

I let the whole fader band show LEVEL's help to see that check fail, and it did. The runtime suite passes with 1517 checks and no failures. clang-format, prettier, build_site.py --check and the lambda scan pass too.

Closes #102