Improve framed width handling and example docs

[evanmschultz]

Summary

• make framed blocks adapt to terminal width and shrink toward content by default
• add regression coverage and goldens for narrow-width table, panel, code block, and log block rendering
• add per-example READMEs, refresh VHS assets, and tighten width/wrap documentation

Testing

• go test ./...
• mage check
• mage vhs