v0.1.0-rc8 Improve Eisenhower, support update person

✨ Features
- tasks: Introduce Eisenhower semantic builder API
  Replaces raw int Eisenhower values with typed Eisenhower constants
  and adds intuitive builder methods (.Important(), .Urgent(),
  .NotImportant(), .NotUrgent()) that compute the correct quadrant at
  create/update time. Consumers can now use:
      client.NewTask("x").Important().Urgent().Create(ctx) // DoNow
      client.NewTask("x").Important().Create(ctx)           // DoLater
  Reading tasks also benefits from helper methods:
      task.Eisenhower.IsImportant()
      task.Eisenhower.IsUrgent()
- people: Add update person endpoint

🧪 Tests
- integration: Add live API validation tests Adds build-tagged
  integration tests that run against the live Lunatask API. Requires
  LUNATASK_API_KEY and LUNATASK_TEST_AREA environment variables. Tests
  cover ping, list operations, and full create/read/update/delete
  round-trips for tasks and notes.  Also excludes dupl and goconst
  linters from test files and updates coverage badge.
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