fix(prompt): anchor active-profile hint at HERMES_HOME, not a nested path

[33hodl]

Summary

When a named profile is active, HERMES_HOME is already profile-scoped (e.g. ~/.hermes/profiles/setup-radar-lab), but agent/system_prompt.py's active-profile hint appended /profiles/<name>/ again, fabricating a non-existent nested path like:

~/.hermes/profiles/setup-radar-lab/profiles/setup-radar-lab/

Agents in profile-scoped desktop sessions were told their session reads/writes a phantom directory. The session's own data actually lives at HERMES_HOME itself; the default profile's data lives under the root (parent of profiles/).

Change

• Active-profile hint now says the session reads/writes HERMES_HOME directly.
• The default profile's data is anchored at get_default_hermes_root() instead of being mis-derived from the profile-scoped home.
• Regression test test_profile_prompt_no_nested_profiles_path covers the non-default profile branch.

Test plan

python -m pytest tests/agent/test_system_prompt.py -o 'addopts=' -q
# 11 passed (incl. new regression test)

[alt-glitch]

This was generated by AI during triage.

Duplicate of #74979: current diffs repair the same doubled named-profile path using the same HERMES_HOME/default-root model. #74979 is the older open implementation with broader integration coverage.

[33hodl]

Closing as a duplicate of #74979, which fixes the same doubled-profile-path defect with stronger integration tests that drive the real resolver chain (this PR mocked the resolver instead). Deferring to that PR — thanks for the thorough work there.