Harden avatar selection and loading for posecode#124

[a-baran-orhan]

Follow-up fixes for posecode-dev/posecode#124.

The original PR branch does not allow maintainer edits, so this draft targets edicate/posecode:main. Merging it into that branch will update posecode-dev#124 while keeping @edib as the original PR author.

What this fixes:

• keeps rig humanoid as skeleton topology and adds a separate optional avatar avatar1|avatar2|avatar3 appearance selector;
• makes character swaps latest-request-wins, disposes stale async loads, supports retry after failure, and always restores the procedural fallback;
• preserves fixed characterUrl behavior and character="off" embed behavior;
• maps avatar1 to the existing XBot instead of committing a duplicate;
• reduces avatar3 from about 35 MB to 7.4 MB;
• adds parser/editor/LSP coverage, lifecycle race tests, generated docs, and a changeset;
• removes unrelated lockfile, roadmap typo, and playground path drift;
• extends the renderer peer range so the additive parser release stays a minor 0.5.0 release instead of cascading to 1.0.0.

Validation:

• npm test: 47 files, 463 tests passed
• npm run typecheck
• npm run build
• npm run build:packages
• npm run check:packages
• npm run eval: 1620/1620 checks across 77 movements
• both new GLBs contain a skin and every required Mixamo bone

Still required before posecode-dev#124 is merged: confirm the source/license provenance for avatar2 and avatar3 and add the appropriate third-party notice. The GLB metadata does not contain enough information to establish this safely.