[codex] document character onboarding and platform next steps

[meekmachine]

What changed

• reframes the model inspection docs around the character onboarding problem: upload a GLB, inspect what is actually in it, choose a preset, validate fit, correct mapping names, and save a reusable profile
• adds a README reading path for uploading/onboarding a new character
• adds a character upload preflight example showing extractFromGLTF, collectMorphMeshes, suggestBestPreset, generateMappingCorrections, validateMappingConfig, validateMappings, and analyzeModel working together
• keeps the API-level return-shape documentation for MappingConsistencyResult, ModelData, ValidationResult, correction results, preset compatibility, and best-preset selection
• adds a May 2026 progress snapshot to VISION_AND_PRD.md, connecting recent Loom3, LoomLarge, and Polyester/Latticework progress to the larger character-platform direction
• adds a concrete next-step sequence: onboarding/preflight, profile-backed behavior assets, authored morph pipeline, runtime-core extraction, and clearer three-layer offering

Why

The original update documented helper methods but did not explain the larger user workflow. These APIs matter because they let Loom3 and LoomLarge turn unknown character asset internals into a validated semantic profile. Once that profile exists, users and AI-driven workflows can control a character through expressive intent, such as AUs, visemes, gaze, head movement, emotes, poses, authored morphs, and expression clips, instead of manually wiring rig-specific morph and bone names.

The vision update also captures what the recent project work is teaching us: profiles are the product contract; preflight is the start of character rigging; AI authoring needs previewable, structured, minimal patches; and runtime portability should be extracted in vertical slices around proven workflows.

Validation

• rebased onto current origin/main after Loom3 PR Harden runtime morph authoring #160
• git diff --check origin/main...HEAD
• README/VISION docs-only change; package typecheck/tests not run because no code changed and this isolated worktree has no node_modules

[meekmachine]

Full triage — REWORK before merge

Keep Embody onboarding/preflight docs; drop Latticework/agency framing. SoM/agencySociety → Polymer/LoomLarge.

Plan: https://github.com/meekmachine/Polymer/discussions/59

[meekmachine]

PR backlog triage — DRAFT_KEEP / REWORK

Drop Latticework/agency framing before merge; Embody onboarding docs OK.