Document AI-optimized mutation workflows

[deverman]

Summary

• Adds docs/mutation-workflows.md covering the full v1 mutation surface for CLI and MCP clients.
• Documents the patch vs lifecycle/status vs move split, homogeneous bulk-only rule, ID-only targeting, previewOnly, verify, and compact returnFields.
• Updates README examples and tool reference with safe mutation workflows.
• Updates use cases and MCP best practices now that v1 write tools exist.

Stack / merge order

Depends on PR #51. Merge order remains:

1. Improve bridge timeout diagnostics #49
2. Implement move_projects folder moves #50
3. Refactor bridge mutation helpers #51
4. this PR

Notes

• The mutation guide explicitly calls out that folder IDs are not exposed by a dedicated v1 read tool yet, so move_projects folder moves require an already-known folder ID. Root-library moves omit destinationID.

Validation

• swift test
• git diff --check

Refs #36

[deverman]

Stack note: this PR is intentionally based on #51. Merge #49 first, then #50, then #51, then #52.