fix(cli): list amp and every --platform value in graphify --help

The top-level help left out the `amp install` / `amp uninstall`
subcommands, and its `install --platform` list omitted copilot, kilo and
kimi, although all of them are accepted (`_PLATFORM_CONFIG`) and
documented in the README platform table. `graphify install` with a bad
platform already prints the full list, derived from `_PLATFORM_CONFIG`;
only the hand-written banner had drifted.

(cherry picked from commit 6480046271)

graphify/__main__.py

@@ -861,7 +861,7 @@ def _run_cli() -> None:
         print("Usage: graphify <command>")
         print()
         print("Commands:")
-        print("  install [--platform P]  copy skill to platform config dir (claude|windows|codebuddy|codex|opencode|aider|amp|agents|claw|droid|trae|trae-cn|gemini|cursor|antigravity|hermes|kiro|pi|devin)")
+        print("  install [--platform P]  copy skill to platform config dir (claude|windows|codebuddy|codex|opencode|aider|amp|agents|claw|droid|trae|trae-cn|gemini|cursor|antigravity|hermes|kiro|pi|devin|copilot|kilo|kimi)")
         print("  uninstall               remove graphify from all detected platforms in one shot")
         print("    --purge                 also delete graphify-out/ directory")
         print("  path \"A\" \"B\"            shortest path between two nodes in graph.json")
@@ -1032,6 +1032,8 @@ def _run_cli() -> None:
         )
         print("  aider install           write graphify section to AGENTS.md (Aider)")
         print("  aider uninstall         remove graphify section from AGENTS.md")
+        print("  amp install             copy graphify skill + write AGENTS.md section (Amp)")
+        print("  amp uninstall           remove graphify skill + AGENTS.md section (Amp)")
         print(
             "  copilot install         copy graphify skill to ~/.copilot/skills (GitHub Copilot CLI)"
         )