docs: plainer SUPPORT and SECURITY, and a dash-free canonical AGENTS.md paragraph

[lesnik512]

Finishes the humanizer pass on the org's prose files and fixes a drift the earlier passes caused.

Appendix B of the standard had "The justfile is the source of truth — just --list, or read it." FL2 requires every AGENTS.md to carry that paragraph word for word. The repo-by-repo dash removals settled on two different replacements: 15 repos use a colon, 11 use a colon plus "run", and release-scope still has the dash. This PR makes the canonical text the colon version, "is the source of truth: just --list, or read it.", because it is the smallest change and the majority already uses it. Separate one-line PRs bring the other 12 repos into line.

Other changes:

• SUPPORT.md: the bold-label bullets ("Documentation:" and so on) are now plain "For X, ..." bullets, and the two dashes are gone.
• SECURITY.md: removed emphasis bold. The bold on the GitHub UI labels ("Security" tab, "Report a vulnerability") stays.

Deliberately unchanged: the rest of docs/standard.md, where the bold marks RFC 2119 keywords, the defined term "core" and table cells, and CODE_OF_CONDUCT.md, which is the stock Contributor Covenant.

uv run pytest passes (175 tests) and mkdocs build --strict is clean.