LaTeX octave diacritics have inconsistent visual weights

[jon-myers]

Issue Description

The latex_octaved_sargam_letter property introduced in v0.1.14 creates visually inconsistent diacritical marks for upper vs lower octaves.

Current Behavior

• Upper octaves (oct +1, +2, etc.): Uses $\dot{\mathrm{letter}}$ - produces clean, thin dots above letters
• Lower octaves (oct -1, -2, etc.): Uses $\underset{\bullet}{\mathrm{letter}}$ - produces bold, thick bullet symbols below letters

Visual Impact

When rendered in matplotlib visualizations, the lower octave marks appear noticeably bolder and more prominent than the upper octave marks, creating visual inconsistency.

Example

from idtap.classes.pitch import Pitch

# Upper octave - thin dot
p_upper = Pitch({'swara': 'ma', 'oct': 1, 'raised': True})
print(p_upper.latex_octaved_sargam_letter)  # $\dot{\mathrm{M}}$

# Lower octave - bold bullet  
p_lower = Pitch({'swara': 'ma', 'oct': -1, 'raised': True})
print(p_lower.latex_octaved_sargam_letter)  # $\underset{\bullet}{\mathrm{M}}$

Suggested Fix

Consider using \underset{\cdot} instead of \underset{\bullet} for lower octaves to match the visual weight of the upper octave dots.

Context

This was discovered while implementing cyclic visualizations that use the new LaTeX diacritics feature. The inconsistent visual weights make the lower octave markings appear disproportionately prominent.