Spike: `flagsmith skills`

We'd like to add a skills installer for all popular LLM harnesses, but first we need to understand what basic set of skills we'd like to ship with.

No files, tests, or entry points are named. Start by surveying the CLI's current command structure and the popular LLM harnesses the issue targets, then define the basic skills set and supported harness scope; done means a documented proposal that can guide a later installer implementation.

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