revise thought-with-image post: add COVT as path 3, mixture becomes path 7

add thought-with-image post: six paths to visual reasoning, no winner

add agent-core post: two definitions of agent in 2026

fix math passthrough, add SVG diagrams, polish vertical-llm-cpt copy

remove personal context from blog posts

add CPT methods blog post for vertical-domain LLM training

refactor: support multiple posts with posts/ directory and add agent frameworks blog