feat(cli): add Hermes agent backend

[rquezada-tech]

Summary

Adds Hermes Agent by Nous Research as a supported agent runtime alongside Claude Code, Codex, and OpenCode.

What changed

• New HermesBackend class in src/cli/daemon/agent/hermes.ts — spawns hermes chat -Q -q <prompt> for non-interactive task execution
• Parses session_id from stdout for session tracking (Hermes outputs this as first line in quiet mode)
• Supports --model flag passthrough and HERMES_PROFILE env var for profile-based execution
• Registered in createBackend() factory and detectRuntimes()
• Updated README BYO Agent table: Hermes moves from "Coming Soon" → "Available"
• 26 new tests covering parseLine, backend execution (mocked spawn), and factory registration

Design decisions

• Lifecycle: per_turn — each task spawns a fresh Hermes process (like OpenCode). Hermes does not yet have a persistent streaming JSON mode equivalent to Claude's --output-format stream-json or Codex's JSON-RPC transport.
• No stdin steering or busy-delivery in this initial version — these require structured output from Hermes CLI. Marked as busyDeliveryMode: "none" and supportsStdinNotification: false.
• The backend is designed to be easy to upgrade when Hermes adds streaming structured output.

Test plan

• All 26 new tests pass
• Full CLI test suite passes (1023 tests, 0 failures)
• Typecheck passes (pnpm typecheck)
• Lint passes

Screenshots

N/A — backend change only.

Closes #N/A (new feature, no existing issue)