[reka18]

What this change does

Domain effects now reach the handler from Start, Tick and RunService, not only Fire. Stacked on #234.

• Every step path goes through one commitStep: append, dispatch, then checkpoint.
• A failed dispatch fails the Handle before its checkpoint. Recover retries the effect, and fails with ErrEffectDispatch while the handler still does. This changes behavior: a Fire after a failed dispatch used to be accepted.
• Start encodes the baseline, applies the initial entry's effects, then writes the baseline, and applies none if the entry failed. Those effects are at-least-once: a handler failure, a failed baseline write or overlapping Start calls re-apply them. Nothing can re-derive them after the baseline.
• New durable.EffectInstance(ctx) gives a handler the instance, because effect ids repeat across instances (durable: defects found in the platform-redesign review #214 question 5). The proposed answer was to add the instance to the effect id. This takes the issue's other option and passes the instance to the handler, so the dispatched set needs no migration.
• New state.ServiceRunner.WithResultTransform, an additive change to the frozen state module. durable uses it so a service result reaches Assign in its decoded form live as well as on replay. Without it, a retried effect could differ from the first attempt under the same id.
• A KindedEffect that can't marshal now fails Tick and RunService, as it already failed Fire, even with no handler wired.

Please check these:

• Departs from the proposed answer to durable: defects found in the platform-redesign review #214 question 4 ("Recover now, redispatch later"): the Handle stops, and Recover fails while the handler is down. A handler that always refuses an effect wedges the instance. This needs a ruling.
• Question 3: a handler on a Store that isn't a DispatchStore still silently applies nothing, now on four paths instead of one. The proposed answer is to refuse the configuration.
• Not fixed: effects from a parent transition an actor drives, including during Fire, aren't dispatched. ActorSystem drops those results, so this needs a state change. durable: defects found in the platform-redesign review #214 lists it.
• Decoding live changes what a service's Assign sees: a struct arrives as a map, an integer as a float64 that loses precision above 2^53, and an error loses its type. The journal records the decoded value.
• A handler's error now matches through errors.Is.
• The first Recover of an older journal applies effects from uncompacted Tick and service steps, which were never dispatched.
• A failed MarkDispatched fails the Handle, and Recover applies that effect again.

Why

Effects from entry, timer and service transitions never reached the handler, and a failed effect could be compacted away and never retried.

Relates to: #214

Evidence

On GOTOOLCHAIN=go1.27.3, in durable unless the row says otherwise:

Command	Result
go test . in state	Pass. It has no direct test of WithResultTransform; durable exercises it
go test ./...	Pass, including TestRunner_EffectDispatch_Start_AppliesEntryEffect, _TimerTransition_AppliesEffect, _ServiceSettle_AppliesEffect and _FailedThenCheckpointed_AppliedOnce

Checklist

• Commits are signed off (git commit -s) per the DCO
• Conventional commit messages (type: subject)
• mage check passes locally (lint + race tests + govulncheck): not run as a whole
• Tests added/updated for the change
• Public API changes documented (godoc) and, if applicable, noted for the changelog

[reka18]

Review results. One reviewer per dimension, each reading the others' findings. All seven dimensions have zero blockers on the latest round.

Fixed along the way: EffectInstance replaced advice to dedupe on an id that repeats across instances. The docs now state when an effect can apply twice, and that a service result reaches Assign JSON-decoded, with an integer losing precision above 2^53. examples/fooddelivery accepts the decoded amount. The four effect-dispatch tests moved here from #213.

For a maintainer: questions 3 and 4 on #214 still need a ruling. The description says where this PR departs from the proposed answers.