Fix Threadleaf navigation icon

[windzu]

What changed

• use a visible monochrome gem icon for the Threadleaf sidebar tab and ribbon
• keep the colored Obsidian crystal on the floating page button
• prepare release 0.1.3

Root cause

The logo-crystal brand asset becomes invisible in the monochrome sidebar tab header.

Validation

• npm run typecheck
• npm test -- --run (48 tests)
• npm run build
• real Obsidian 1.12.7 verification of the right sidebar tab and left ribbon