Add include_prompts_in_repositories whitelist for prompt storage

[jwiegley]

Summary

• Adds include_prompts_in_repositories config option to whitelist repositories for enterprise prompt storage (CAS)
• Adds default_prompt_storage config option to specify fallback storage mode for non-whitelisted repos
• Adds PromptStorageMode enum for type-safe handling of storage modes
• Updates effective_prompt_storage() resolver to handle the new whitelist logic with proper precedence

Motivation

This enables two common use cases:

User A (wants git-ai everywhere, CAS for work repos, notes for OSS):

{
  "prompt_storage": "default",
  "include_prompts_in_repositories": ["https://github.com/myorg/*"],
  "default_prompt_storage": "notes"
}

User B (wants git-ai only for work repos with CAS):

{
  "prompt_storage": "default",
  "allow_repositories": ["https://github.com/myorg/*"],
  "include_prompts_in_repositories": ["*"]
}

Changes

• src/config.rs: Added PromptStorageMode enum, new config fields, effective_prompt_storage() resolver, and tests
• src/authorship/post_commit.rs: Updated to use new effective_prompt_storage() resolver
• src/commands/config.rs: Added CLI support for get/set/unset of new config options

Test plan

• Added unit tests for PromptStorageMode::from_str() and as_str()
• Added unit tests for effective_prompt_storage() covering:
  • No include list uses global prompt_storage (legacy behavior)
  • Exclude list always wins (returns Local)
  • Wildcard include matches repos without remotes
  • Non-wildcard include with no match uses fallback
  • No fallback configured defaults to Local
  • Pattern matching works correctly
• All existing tests pass

🤖 Generated with Claude Code

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[jwiegley]

Hmm… When I click on the signing link, it says that I have signed the agreement, but it is not showing up in the status here…

[acunniffe]

Seems to be working now. I've never see it do that before.

[jwiegley]