feat: load AGENTS.md from profile directory first, fall back to cwd

[xmhcte]

Currently AGENTS.md is only loaded from the workspace/cwd directory. For multi-profile setups (e.g. distinct role rules per profile), each profile needs its own AGENTS.md with role-specific constraints.

This change introduces a profile-first lookup: get_hermes_home()/AGENTS.md takes priority, cwd/AGENTS.md serves as fallback. This mirrors the existing SOUL.md loading pattern.

[teknium1]

Thanks for the focused profile-context proposal.

Problems

• agent/prompt_builder.py:1685 returns profile AGENTS.md before checking the workspace. That suppresses a repository's project instructions whenever the profile file exists. Current main documents AGENTS.md as CWD project context (website/docs/user-guide/features/context-files.md:16,28-32) and reserves $HERMES_HOME/SOUL.md for profile-wide identity (website/docs/user-guide/features/personality.md:32-47). Commit 725831171 also deliberately limited AGENTS startup lookup to the working-directory root.
• The PR changes this resolution contract without tests. Main's existing contract test is tests/agent/test_prompt_builder.py:758-766; no profile-vs-workspace precedence or fallback test is included.

Suggested changes

• Please have maintainers settle the desired profile-wide instruction surface and its precedence relative to workspace instructions before changing this loader. If profile-level AGENTS is adopted, document the resulting contract and add hermetic tests for profile-only, workspace-only, both-present, and empty-profile cases.

Automated hermes-sweeper review.

[teknium1]

This precedence makes a profile AGENTS.md suppress the workspace AGENTS.md rather than fall back to it. Current main treats AGENTS.md as CWD project context and HERMES_HOME/SOUL.md as profile-wide identity; please settle and document the intended source-of-truth/precedence before changing this branch.