docs: clarify multi-worktree index scope workflow

[DxTa]

Summary

• Add a clear multi-worktree and multi-agent setup section in README.md with scope resolution order and practical workflow steps.
• Document shared vs worktree index modes in docs/INDEXING.md, including writer/read concurrency guidance.
• Expand docs/LLM_CLI_INTEGRATION.md with setup recommendations for multiple Claude Code instances.

Verification

• Markdown local-link validation script across all *.md files (OK).

🤖 Generated with Claude Code

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Add branch-creation flag to worktree example

The workflow command git worktree add ../feat-auth feat/auth will fail for users who are creating a new feature branch, because feat/auth is treated as an existing <commit-ish> unless -b/-B is provided. git worktree add -h documents this as git worktree add ... [(-b | -B) <new-branch>] <path> [<commit-ish>] and explicitly says -b <branch> create a new branch, so the current example is not copy-paste safe in the common “new branch” scenario.

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