refactor: review 0.14 for duplication, deprecated calls and plain docs

[vdmkenny]

A review of the whole 0.14 diff (v0.13.0..main) for quality, duplication and CONTRIBUTING.md, plus the same clean-ups in the older code.

Code from 0.14:

• Mouse.pixelsIn converts the pointer to pixels. The CD player's canvas, the HUD options menu and the scripts' pointer field each did this conversion themselves.
• recordingStem uses recordings.Kind.of instead of its own loop.
• recordings.Source logs a recording it leaves out in one place.
• The CD player's track limit (96) comes from the two digits a row's number has, instead of a bare 8.
• A comptime check ties records.room_views' fields to rooms.View.
• An FFmpeg packet larger than a c_int fails with an error instead of a panic, since a FLAC file is sent whole.

Across the tree:

• std.mem.print and Allocator.print replace every std.fmt.bufPrint and std.fmt.allocPrint call, which Zig 0.17 deprecates.
• Byte sizes written as shifts or products (256 << 20, 16 * 1024 * 1024) use std.fmt.parseIntSizeSuffix, as the 0.14 code does. Three unnamed limits get names.
• Messages print those sizes with {Bi} instead of spelling them out, so they can't disagree with the constant.
• The game, player and load scripts share one per-mod memory limit, runtime.memory_per_mod. The tests share runtime.testing.options instead of seven copies of the same options.

Text:

• Comments, docs and API strings from 0.14 rewritten in plain English. make definitions regenerated the reference.
• "Added by OpenReliant:" replaces the second marker for additions, "Not the game's:".

No behaviour changes, apart from three messages that now print sizes as 16MiB rather than 16777216 bytes or 8 MiB.

Left as they are: scratch buffers in the dev tools ([16 << 10]u8) and sizes inside test data, where the arithmetic is the point.