feat(kimi): add Kimi Code CLI adapter with opt-in hooks

[blankanswer]

Summary

• Add a Kimi Code CLI agent adapter for Gortex.
• Support project-local Kimi MCP setup through gortex init --agents=kimi, writing .kimi-code/mcp.json.
• Support explicit user-level Kimi integration through gortex install --agents=kimi, writing Kimi MCP config and the UserPromptSubmit hook.
• Route Kimi hooks through gortex hook --agent=kimi and reuse the existing UserPromptSubmit symbol-context enrichment.
• Keep Kimi hook output plain stdout, matching Kimi's hook behavior instead of Claude-style additionalContext JSON.
• Part of Add support for Kimi code cli with pretool use/post tool use hooks for context injection #214.

Design notes

• init remains repo-local and team-shareable; it does not mutate ~/.kimi-code/config.toml.
• install is the explicit local-machine action that enables the user-level Kimi hook.
• The user-level Kimi hook no-ops outside Gortex-enabled projects before probing the daemon.
• A project is considered Gortex-enabled when the hook cwd is under one of:
  • .kimi-code/mcp.json containing mcpServers.gortex
  • .gortex.yaml
  • a Gortex-managed .gortex/.gitignore marker
• Kimi prompt payloads support both plain string prompts and text content parts.
• Existing Claude, Gemini, Codex, and Antigravity behavior remains unchanged.

Out of scope

• Stop
• subagent hooks
• PreToolUse
• PostToolUse
• deny / enforcement behavior
• permission decisions
• input rewrite
• output suppression
• resolver / indexer / daemon / graph / MCP tool changes

Tests

• go test ./internal/agents/... -count=1
• go test ./internal/hooks -count=1 -timeout=180s
• go test ./cmd/gortex -count=1 -timeout=300s
• go test ./internal/hooks -run 'TestRunKimi|TestKimi' -count=1 -timeout=120s -v
• git diff --check -- internal/hooks/kimi.go internal/hooks/kimi_test.go
• Added coverage for Kimi project-local MCP rendering, user-level hook install, plain stdout hook output, content-part prompt handling, and project-outside no-op behavior.