Support project-level configure scope

[codeprakhar25]

What problem does this solve?

AgentDiff setup is currently mostly global. That is convenient for personal use, but teams may want repo-scoped configuration that can be reviewed, versioned, and enforced per project.

The main question: should agentdiff configure support project-level agent setup, or should project-level guidance live in files like AGENTS.md, .cursor/skills/, and repo-local config only?

What would you like to see?

Explore and add project-level configuration support.

Possible CLI shape:

agentdiff configure --scope global
agentdiff configure --scope project
agentdiff configure --scope project --agents cursor,codex

Possible project-level outputs:

• repo-local AgentDiff config under .agentdiff/ or .git/agentdiff/
• repo-local agent guidance such as AGENTS.md
• project Cursor skill installation
• repo-local VS Code workspace settings where applicable
• clear docs for which integrations cannot be made project-local because the agent only supports global hooks

Open questions

• Which agents actually support project-local hooks/settings?
• Should AGENTS.md become the canonical cross-agent instruction surface?
• Should project-level configure write files into the worktree, or only into .git/agentdiff/?
• How do we avoid surprising users by modifying repo files?

Acceptance criteria

• There is a documented distinction between global and project-level setup.
• The CLI can run project-level setup without overwriting unrelated files.
• Project-level setup is safe to review in a PR when it writes worktree files.
• Agents that cannot be configured per-project are reported clearly.

Alternatives considered

Only keep global configure and add docs. That is simpler, but weaker for teams and experiments where every agent should receive the same repo-level instruction.