feat: add the Hermes Agent preset

[RAIT-09]

Description

Add Hermes Agent (Nous Research) as the seventh preset agent.

• Registry entry only — no per-agent code elsewhere. The preset spawns hermes with the acp argument (ACP server mode, available since Hermes Agent v0.2.0).
• Login-only preset: Hermes manages provider credentials itself (hermes model / hermes setup --portal) and has no single official API-key environment variable, so the preset shows no API key field (same as OpenCode).
• No custom-agent absorption: the docs never prescribed a custom-agent id for Hermes, so existing custom entries are left untouched. A custom agent with the id hermes-agent is renamed to hermes-agent-2 by the existing collision handling, and the setup page explains how to migrate manually.
• New setup page (docs/agent-setup/hermes.md) plus listings in the agent tables, FAQ, troubleshooting, README (en/ja), and AGENTS.md. Install instructions point to the official install scripts only — the hermes-agent package on npm is third-party and deliberately not referenced.

Related issue

None

Type of change

• Bug fix
• New feature
• Documentation
• Refactor
• Other

Checklist

• npm run lint passes ("Use sentence case for UI text" errors are acceptable for brand names)
• npm run build passes
• Tested in Obsidian
• Existing functionality still works
• Documentation updated if needed

Testing environment

• Agent: Hermes Agent (v0.18.2)
• OS: macOS

Screenshots

N/A

Summary by CodeRabbit

• New Features
  • Added Hermes Agent as a built-in ACP agent preset.
  • Added installation, configuration, authentication, troubleshooting, and verification guidance for Hermes Agent.
  • Added Hermes Agent to supported-agent lists, setup links, navigation, FAQs, and context-file documentation.
• Documentation
  • Updated English and Japanese getting-started materials to include Hermes Agent.
• Tests
  • Updated agent availability checks to include Hermes Agent.

[coderabbitai]

📝 Walkthrough

Walkthrough

Hermes Agent is added as a built-in ACP preset with installation and authentication guidance. Agent enumeration tests, navigation, README files, setup documentation, FAQs, troubleshooting, and supported-agent references are updated accordingly.

Changes

Hermes Agent integration

Layer / File(s)	Summary
Preset registry and enumeration validation src/services/preset-agents.ts, test/session-helpers.test.ts	Registers the hermes-agent preset with its command, installation instructions, settings copy, and documentation reference; updates agent enumeration fixtures and expectations.
Setup documentation and navigation docs/agent-setup/hermes.md, docs/.vitepress/config.mts, docs/agent-setup/index.md, docs/help/troubleshooting.md	Adds Hermes Agent setup, navigation, installation, authentication, migration, and connection verification guidance.
Documentation and README coverage AGENTS.md, README.md, README.ja.md, docs/getting-started/quick-start.md, docs/help/faq.md, docs/index.md, docs/reference/acp-support.md, docs/usage/context-files.md	Lists Hermes Agent among supported presets, ACP agents, context-file options, and setup resources.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• RAIT-09/obsidian-agent-client#348: Introduced the registry-driven preset-agent system extended by this change.
• RAIT-09/obsidian-agent-client#349: Overlaps in preset registration and session-helper enumeration coverage.
• RAIT-09/obsidian-agent-client#365: Adds another built-in preset using the same registry and test patterns.

Poem

I’m a bunny with a Hermes guide,
Through ACP I hop and glide.
hermes ac begins the play,
Auth is set in its own way.
Seven presets now bloom bright—
Docs and tests all point it right!

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title is concise and accurately summarizes the main change: adding the Hermes Agent preset.
Description check	✅ Passed	The description matches the template well and includes all required sections with concrete details.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/hermes-agent-preset

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