refactor(cli): move species identity from docs into sol call identity hydrate
The species prose was being copied verbatim into every journal's AGENTS.md via the seeding maint task, recreating the static-identity-in-a-doc problem the earlier identity retreat was meant to solve.
Move that prose to an authoritative Python constant in think/tools/sol.py, prepend it as a # species section in sol call identity hydrate output, and strip duplicate # {stem} headings from section bodies during hydrate composition. Individual subcommand output and on-disk sol/*.md files remain unchanged.
The heading strip is render-time only and case-insensitively matches an exact-stem first heading, so custom first-line headings in user files are preserved.