fix(learn): name distilled skills as author Hermes, not the host OS user (#52388)

/learn told the agent to fill the skill `author` field, and the system
prompt environment probe surfaces the OS login name (user=$(whoami) in
prompt_builder.py), so the model wrote the host username into published
SKILL.md frontmatter — a privacy leak the user never opted into, and
inconsistent run to run as the most-salient identity changed.

The /learn authoring prompt now sets `author` to the literal value
`Hermes` and explicitly forbids deriving it from the host environment
(OS/login user, git config, or any probeable identity). The skill names
itself as the tool that wrote it.

Closes #52368.

agent/learn_prompt.py

@@ -46,8 +46,11 @@ Frontmatter:
     Bad (123):   `A comprehensive skill that lets the agent search arXiv for
                   academic papers using keywords, authors, and categories.`
 - version: 0.1.0
-- author: the human you are authoring this for, first; "Hermes Agent" second.
-  Never credit only the tool.
+- author: always the literal value `Hermes`. NEVER fill it from the host
+  environment — the OS/login username (e.g. the `user=` line in your
+  environment hints), git config, or any identity you can probe must not be
+  written. Skills get shared and published, so an environment-derived name is
+  a privacy leak the user never opted into; the skill names itself as Hermes.
 - platforms: declare `[macos]`, `[linux]`, and/or `[windows]` IF the skill
   uses OS-bound primitives (osascript/apt/systemctl => the matching OS; /proc,
   os.setsid, signal.SIGKILL => linux; fcntl/termios => POSIX). Prefer fixing it