Add clickup changes command for tracking workspace updates

[pikonha]

Summary

Adds a new clickup changes command that lists tasks and docs updated in a workspace since a point in time. This enables users to quickly see what changed since their last visit, with automatic state tracking per workspace.

Changes

• New clickup changes command (cmd/changes.go):

  • Lists tasks and docs updated since a specified point in time
  • --since flag accepts: last (tracked per workspace), durations (30m, 24h, 7d, 2w), dates (2026-06-09), RFC3339 timestamps, or Unix milliseconds
  • Tasks filtered server-side via date_updated_gt parameter with automatic pagination (up to 5,000 tasks)
  • Docs filtered client-side by date_updated (falling back to date_created) since the v3 Docs API lacks server-side filtering
  • Supports --skip-docs, --no-save, --space-ids, --folder-ids, --list-ids flags
  • Returns JSON with workspace ID, since/until timestamps, task/doc counts, and full objects

• State management (internal/config/state.go):

  • New ~/.clickup-cli-state.json file to track the last successful changes --since last run per workspace
  • GetLastChangesCheck() and SetLastChangesCheck() functions for reading/writing state
  • First run defaults to a 24-hour window and sets "first_run": true in output

• API enhancements (internal/api/docs.go):

  • Added DateUpdated field to Doc struct to support client-side filtering

• Comprehensive test coverage (cmd/changes_test.go):

  • Tests for basic command functionality, task query parameters, doc skipping, state tracking, pagination, and error handling
  • Unit tests for parseSince() covering durations, dates, RFC3339, and Unix ms formats
  • Mock HTTP server for testing API interactions

• Documentation:

  • Updated docs/api.md with full command reference, flags, and usage examples
  • Updated AGENTS.md with change tracking workflows and common patterns
  • Updated README.md and CHANGELOG.md with new command

• Test infrastructure fix (cmd/integration_test.go):

  • Fixed potential deadlock in runCommand() by draining stdout concurrently to handle large outputs

Checklist

• go build ./... passes
• go test ./... passes
• go vet ./... passes
• New commands have table-driven tests (TestParseSince and comprehensive integration tests)
• docs/api.md updated with new command, flags, and examples
• Every API parameter has a corresponding CLI flag (--space-ids, --folder-ids, --list-ids, --skip-docs, --no-save)
• Commit messages follow conventional commits

https://claude.ai/code/session_019Aexh4uFP9TfNcm8nD42fN