docs: AGENTS.md routing line and toc.py docstring describe docs/ as the whole human documentation (#187)

Closing-phase pull-through: both still described docs/ by its pre-9.0.0 role.

Files changed:
- AGENTS.md
- CHANGES.md
- VERSION
- tools/chemenu/toc.py

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SnAJ7Z3CpVD3PRbN73QtU2

AGENTS.md

@@ -222,8 +222,9 @@ input       schema + compiler     output   derived (gitignored)
                   work/   tracked scratch, deleted when the run closes
 ```
 
-Alongside it, not part of it: `instructions/` (what agents are told to do), `docs/` (why the
-stack is built the way it is - see [File naming](#file-naming)), and this file.
+Alongside it, not part of it: `instructions/` (what agents are told to do), `docs/` (the stack's
+human documentation, including why it is built the way it is - see [File naming](#file-naming)),
+and this file.
 
 **By stage** - read the contract for the stage you are writing in: