fix: scope apso generate formatting to generated output only (#70)

[cultron]

Closes #70

Problem

apso generate's format step delegated to the target project's npm run format, whose broad glob (e.g. {src,test}/**/*.ts) reformatted the entire project tree on every run — rewriting hand-written code that has nothing to do with code generation.

Fix

• base-command: extract a generic runCommand(command, args, silent); runNpmCommand now delegates to it.
• generate: format via npx prettier --write <rootFolder>/autogen/**/*.ts, scoped to the generated output dir (the stale src/guards glob was unnecessary — guards live under autogen/). Guard formatting on generatedFileCount > 0, and warn when .apsorc defines no entities.

Verification

End-to-end against a throwaway project containing a deliberately mis-formatted hand-written file outside autogen:

• With entities → prettier targeted only …/src/autogen/**/*.ts; the hand-written file was byte-identical afterward (previously it would have been reformatted).
• Build ✅ · lint 0 errors ✅

Note: this change was previously committed onto feat/import-supabase-data (PR #69); it has been moved here as a standalone PR and dropped from that branch so each lands independently.

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