Add support for kiro-cli

[jsyrjala]

It would be nice to have support for Amazon's Kiro CLI.

https://kiro.dev/cli/

[jsyrjala]

Quick AI generated estimate what would be needed for the support.

⏺ Changes needed to add Kiro CLI support

src/cli/cli.h

1. Add bool kiro; to cbm_detected_agents_t struct (line ~117)

src/cli/cli.c

2. Detection (~line 860): Add ~/.kiro/ directory check in cbm_detect_agents()
3. Print (~line 2173): Add if (agents.kiro) printf(" Kiro");
4. None guard (~line 2182): Add && !agents.kiro to the condition
5. Install step (line 2370): Add Kiro block calling cbm_install_editor_mcp(self_path, "/.kiro/settings/mcp.json")
6. Uninstall (~line 2420): Add Kiro block calling cbm_remove_editor_mcp() for the same path
7. Help text in src/main.c line 138: Add "Kiro" to the supported agents list

tests/test_cli.c

8. Add a detection test for Kiro (follow existing pattern for other agents)

Total: ~30 lines of new code across 3-4 files, all following established patterns. No new functions needed — reuses cbm_install_editor_mcp() / cbm_remove_editor_mcp().