feat: add harmony and audiowave timeline kinds to CLI add command

[FelipeDefensor]

Summary

• Adds harmony / har and audiowave / aud as valid kind arguments to timelines add.
• Harmony timelines omit the --height kwarg (their height is computed from level count and level height internally).
• Audiowave timelines similarly omit --height.
• Tests added for both new kinds and their abbreviations.

Test plan

• tilia timelines add harmony --name "Chords" creates a harmony timeline.
• tilia timelines add har works as shorthand.
• tilia timelines add audiowave --name "Wave" creates an audiowave timeline.
• tilia timelines add aud works as shorthand.

Closes #476

[FelipeDefensor]

Superseded by #575.

This branch was cut ~209 commits before current dev and no longer merges — the TimelineKind enum it's written against has since been removed in favour of Timeline subclasses, and add.py was restructured around that.

Review also turned up that the audiowave kind could not have worked from the CLI at all: create_timeline calls AudioWaveTimeline.refresh(), which requests Get.PLAYBACK_AREA_WIDTH — served only by QtUI. With media loaded it raised NoReplyToRequest and left an empty timeline behind; without media it produced a hidden, empty one. The tests here passed because they never loaded media and asserted only kind and name, both of which hold for a hidden empty timeline.

#575 reimplements this on dev with that fixed, adds pdf so #476 actually closes, and rejects --height for harmony instead of silently dropping it.