feat: add Hermes and Crush AI agent backend support

[im47cn]

Summary

Adds support for two new AI coding agents:

• Hermes (NousResearch) — ACP-based agent, spawned via hermes acp
• Crush (Charmbracelet) — HTTP server agent, spawned via crush server

Changes

happy-cli (packages/happy-cli/)

Hermes (ACP — minimal changes):

• Added hermes to KNOWN_ACP_AGENTS in acpAgentConfig.ts → hermes acp
• Added hermes case to daemon agent spawning (routes through happy acp hermes)
• CLI subcommand happy hermes delegates to the generic runAcp() runner
• Added 'hermes' to resolveSessionFlavor() and BackendFlavor

Crush (custom backend — follows Agy pattern):

• src/crush/CrushBackend.ts — AgentBackend impl that spawns crush server with a Unix socket, communicates via REST API + SSE
• src/crush/runCrush.ts — Session runner following the runAgy.ts pattern
• Static mapEvent() method for testable event-to-AgentMessage mapping
• CLI subcommand happy crush and daemon spawn case

Shared:

• AgentId type includes 'hermes' | 'crush'
• SpawnSessionOptions.agent includes new types
• BackendFlavor includes new types

happy-app (packages/happy-app/)

• agentDefaults.ts: agentKeys array + normalizeAgentKey() + defaults
• persistence.ts: NewSessionAgentType includes new agents
• ops.ts: SpawnSessionOptions.agent includes new types
• AgentInput.tsx: agentType prop type
• Session info: displays "Hermes" / "Crush" as provider names

Tests (31 new tests)

• acpAgentConfig.test.ts — Updated to verify Hermes config resolution
• hermes.test.ts — Hermes ACP config, args passthrough
• CrushBackend.test.ts — All 19 crush event-to-message mappings

Test Files  3 passed (3)
     Tests  31 passed (31)

Usage

happy hermes    # Run Hermes agent (ACP)
happy crush     # Run Crush agent (HTTP server)
happy acp hermes  # Also works via generic ACP command

Design decisions

• Hermes reuses the existing runAcp() infrastructure — only a config entry + CLI wiring needed
• Crush uses a custom CrushBackend (like AgyBackend) since Crush doesn't support ACP
• Event mapping extracted as static mapEvent() on CrushBackend for testability

💘 Generated with Crush

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