feat(project): scaffold add/remove/dev/deploy/status/build commands

[tejaskash]

What

Scaffolds six agentcore project subcommands: add, remove, dev, deploy, status, build.

• Each handler follows the directory-per-command layout with a create<Name>ProjectHandler() factory and throws NotImplementedError.
• Adds NotImplementedError to src/errors, a subclass of AgentCoreCLIError with INTERNAL source.
• No flags, screens, or Core interfaces yet; those land with the real implementations.

Testing

• Parameterized test in project.test.ts asserts each command throws not implemented through the real root handler.
• Full suite: 424 pass, 0 fail. tsc --noEmit and Prettier clean.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.64%. Comparing base (5b9506f) to head (edf8274).

Additional details and impacted files

@@             Coverage Diff              @@
##           refactor    #1857      +/-   ##
============================================
+ Coverage     95.61%   95.64%   +0.03%     
============================================
  Files           181      187       +6     
  Lines          8842     8912      +70     
============================================
+ Hits           8454     8524      +70     
  Misses          388      388              

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[notgitika]

The scaffolding LGTM!