Correct the claim that there is no unschedule

[cardmagic]

Summary

docs/reminders.md said "Solid Objects has no unschedule". The gem has unschedule(operation_or_handle, key:) and unschedule_all(operation) (lib/solid_objects/actor.rb), and test/integration/reminder_cancellation_test.rb covers them. An agent that read the guide was told that a Rails reminder cannot be cancelled.

Changes

• docs/reminders.md: a new section "Cancel a reminder". Each statement in it has a test in reminder_cancellation_test.rb: cancel by operation, key, or handle; unschedule_all; a failed turn cancels nothing; an absent reminder is not an error; an unknown operation raises.
• docs/agents.md: the rules show unschedule(:expire, key: buyer), and the mistakes table lists a guessed cancel method.
• test/unit/reminder_documents_test.rb: fails when the reminder guide does not name a public reminder method of an actor, or denies one.
• CHANGELOG.md: an Unreleased entry.

Compatibility

Documentation and a test only. No code change.

Validation

• The three new tests failed before the change and pass after it.
• bundle exec rake: 961 runs, 0 failures. RuboCop and Steep pass.

[context7]

Docs7 for cardmagic/solid-objects-ruby

Result	Status	Action
Deployment	➖ Not used	—
Content review	➖ Did not run. This site has no agent runs available this month. Wait for the monthly reset or check your Docs7 plan.	—

Commit 908e5ba

[greptile-apps]

Confidence Score: 5/5

[Low impact] The PR appears safe to merge; the previous test issue is fixed and no new actionable issues were found.

Summary

Corrects the reminder cancellation guide and adds tests that check the documented methods.

• Actor authors can now find clear instructions for cancelling reminders.

_{Reviews (2) · Last reviewed commit: "test: require each reminder method name ..." · Reviewed by Greptile}

[cardmagic]

@greptileai Please review the current head 908e5ba. The check now includes the closing backtick, so each reminder method needs its own mention in the guide. The test passes.