fix: reconcile hidden charge base intents

[turip]

Summary

• persist hidden base/source delete, shrink, and extend patches for overridden usage-based and flat-fee charges before entering the charge state machine
• reject hidden base targets inside type-specific state machines so lifecycle code only handles the active customer-facing layer
• add subscription-sync coverage for canceling subscriptions after gathering/standard invoice API deletes create customer-facing overrides

Root Cause

Subscription sync still owns the base/source intent even after an API edit creates a customer-facing override. Follow-up sync patches such as cancellation shrink/delete were entering the effective charge state machine, which correctly saw the override-backed charge as deleted and rejected the base-layer reconciliation.

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR adds a rejectHiddenIntentTarget guard to flat-fee and usage-based charge state machines so lifecycle mutations refuse base-layer targets when an override exists. It also adds base-intent bypass logic to TriggerPatch, extends the Patch interface with GetTargetLayer, removes ShouldReconcile gating in favor of unconditional reconciliation, updates SKILL.md docs, and expands subscription-sync tests.

Changes

Hidden-target rejection and base-intent bypass

Layer / File(s)	Summary
Patch interface and skill docs openmeter/billing/charges/meta/patch.go, .agents/skills/charges/SKILL.md	Adds GetTargetLayer(LayeredIntentReader) (ChangeTarget, error) to the Patch interface and clarifies patch-routing rules for base vs override targeting and delete-patch semantics.
rejectHiddenIntentTarget helper openmeter/billing/charges/flatfee/service/statemachine.go, openmeter/billing/charges/usagebased/service/statemachine.go	Adds a shared-shape method on each state machine that returns a precondition-failed error when a base-layer target is requested while an override layer is active.
Flat-fee state machine updates openmeter/billing/charges/flatfee/service/creditheninvoice.go, .../creditsonly.go	DeleteCharge, ExtendCharge, ShrinkCharge, LineManualEdit, and applyPeriodPatch now call the rejection helper, drop prior override-based early returns, and remove ShouldReconcile from reconciliation input.
Usage-based state machine updates openmeter/billing/charges/usagebased/service/creditheninvoice.go, .../creditsonly.go	Same pattern applied to usage-based DeleteCharge, ExtendCharge, ShrinkCharge, ShrinkToRealizedPeriod, and applyPeriodPatch, removing the ShouldReconcile field from result structs.
Base-intent bypass in TriggerPatch openmeter/billing/charges/flatfee/service/triggers.go, openmeter/billing/charges/usagebased/service/triggers.go, .../usagebased/service/triggers_test.go	Adds applyBaseIntentPatchForOverriddenCharge and mutateBaseIntentPeriodForOverriddenCharge helpers so TriggerPatch can mutate and persist base intent directly, skipping the state machine, with new tests covering shrink and rejection scenarios.
Subscription-sync test coverage openmeter/billing/worker/subscriptionsync/service/sync_credittheninvoice_test.go	Adds cancellation subtests asserting base-intent period reconciliation, retained override IntentDeletedAt, and empty realizations for deleted flat-fee and usage-based charges.

Estimated code review effort: 4 (Complex) | ~60 minutes

Possibly related PRs

• openmeterio/openmeter#4053: Related through the usage-based TriggerPatch logic in triggers.go that this PR extends with base-intent bypass handling.
• openmeterio/openmeter#4607: Directly connected via the layer-aware target computation (GetTargetLayer/ChangeSource) that this PR builds its rejection logic on top of.
• openmeterio/openmeter#4576: Shares the same base-vs-override targeting contract for subscription-sync delete/shrink/extend patches reconciled against hidden base intents.

Suggested labels: release-note/bug-fix, area/billing

Suggested reviewers: tothandras

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly matches the main change: reconciling hidden charge base intents.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/charge-hidden-base-reconciliation

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}