Bill status and support passthrough for unregistered schemas in schema.Object

[samlown]

• Working on support for the bill.Status model.
• Allow schema.Object to preserve raw JSON for schemas not registered in the GOBL registry, enabling external complement types to round-trip without requiring registration
• Add HasPayload() method to distinguish resolved objects from passthrough
• Add envelope validation rule (ENVELOPE-04) ensuring the doc field always has a known/registered schema

Pre-Review Checklist

• Opened this PR as a draft
• Read the CONTRIBUTING.md guide.
• Performed a self-review of my code.
• Added thorough tests with at least 90% code coverage.
• Modified or created example GOBL documents to show my changes in use, if appropriate.
• Added links to the source of the changes in tax regimes or addons, either structured or in the comments.
• Run go generate . to ensure that the Schemas and Regime data are up to date.
• Reviewed and fixed all linter warnings.
• Been obsessive with pointer nil checks to avoid panics.
• Updated the CHANGELOG.md with an overview of my changes.
• Marked this PR as ready for review.

And if you are part of the org:

• Requested a review from Copilot and fixed or dismissed (with a reason) all the feedback raised.
• Requested a review from @samlown.

[codecov]

Codecov Report

❌ Patch coverage is 97.20000% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 93.20%. Comparing base (72beee4) to head (4192797).
⚠️ Report is 17 commits behind head on main.

Files with missing lines	Patch %	Lines
cal/timestamp.go	93.67%	3 Missing and 2 partials ⚠️
bill/status.go	98.62%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #796      +/-   ##
==========================================
+ Coverage   93.09%   93.20%   +0.11%     
==========================================
  Files         368      370       +2     
  Lines       19624    19870     +246     
==========================================
+ Hits        18269    18520     +251     
+ Misses        919      913       -6     
- Partials      436      437       +1     

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[Copilot]

Pull request overview

This PR expands GOBL’s document/model support by introducing bill.Status and cal.Timestamp, and updates schema.Object to allow round-trip passthrough of unregistered $schema payloads while tightening envelope validation to require a registered schema for Envelope.doc.

Changes:

• Update schema.Object to preserve raw JSON for unregistered schemas and add HasPayload() to distinguish resolved vs passthrough objects.
• Add bill.Status model (schema + rules + tests) and new ES status examples/output fixtures.
• Add cal.Timestamp model (schema + rules + tests) and extend CLI/envelope validation expectations (ENVELOPE-04).

Reviewed changes

Copilot reviewed 32 out of 37 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
schema/object.go	Adds raw passthrough storage, HasPayload(), and marshaling/unmarshaling behavior changes.
schema/object_test.go	Updates/extends tests to cover unknown-schema passthrough, round-trip, clone, calculate, and payload detection.
envelope.go	Adds ENVELOPE-04 assertion requiring doc to have a known/registered schema (payload present).
envelope_test.go	Adds validation case for passthrough doc failing ENVELOPE-04.
internal/cli/validate_test.go	Updates expected error output now that unknown schemas passthrough and are rejected by envelope validation.
internal/cli/build_test.go	Updates expected error output for unknown-schema docs to reflect ENVELOPE-04.
cmd/gobl/validate_test.go	Updates expected multi-fault ordering to include ENVELOPE-04.
internal/cli/bulk_test.go	Updates the schema listing fixture to include new bill/status and cal/timestamp schemas.
bill/status.go	Introduces the bill.Status model, normalization, calculation, schema extension, and rules.
bill/status_test.go	Adds comprehensive tests for status calculation, validation, definitions, and schema extension.
bill/bill.go	Registers bill.Status schema/rules and adds ShortSchemaStatus.
data/schemas/bill/status.json	Adds generated JSON Schema for bill.Status and related defs.
data/rules/bill.json	Adds generated rules for bill.Status, StatusLine, Reason, Action, Condition.
examples/es/status-update.yaml	Adds ES example input for status “update”.
examples/es/status-system.yaml	Adds ES example input for status “system”.
examples/es/status-system-shutdown.yaml	Adds ES example input for a system shutdown status.
examples/es/status-system-anomaly.yaml	Adds ES example input including an external complement passthrough object.
examples/es/status-response.yaml	Adds ES example input for status “response”.
examples/es/out/status-update.json	Adds generated envelope output for the status-update example.
examples/es/out/status-system.json	Adds generated envelope output for the status-system example.
examples/es/out/status-system-shutdown.json	Adds generated envelope output for the shutdown example.
examples/es/out/status-system-anomaly.json	Adds generated envelope output for the anomaly example (includes complement passthrough).
examples/es/out/status-response.json	Adds generated envelope output for the status-response example.
cal/timestamp.go	Introduces cal.Timestamp type with JSON (un)marshal, parsing, schema, and rule scaffolding.
cal/timestamp_test.go	Adds tests for timestamp parsing, JSON behavior, string/clone helpers, and validation interactions.
cal/cal.go	Registers cal.Timestamp schema and rules.
data/schemas/cal/timestamp.json	Adds generated JSON Schema for cal.Timestamp.
data/rules/cal.json	Adds generated rules entry for cal.Timestamp.
cal/time.go	Adds Time.IsZero() to support ,omitzero JSON tag behavior.
cal/time_test.go	Adds tests for Time.IsZero() and ,omitzero marshaling.
data/rules/gobl.json	Adds generated envelope rule subset for ENVELOPE-04.
data/schemas/schema/object.json	Updates schema.Object description formatting for $schema.
bill/ordering.go	Updates comments to refer to “document” rather than “invoice” in shared ordering context.
data/schemas/bill/ordering.json	Updates generated ordering schema descriptions accordingly.
bill/invoice.go	Makes Invoice.CanSign() nil-safe.
bill/invoice_test.go	Adds tests for top-level inversion paths, Invoice.Empty(), Invoice.UnmarshalJSON edge cases, and Invoice.CanSign().
CHANGELOG.md	Adds unreleased changelog entries for schema.Object passthrough, bill.Status, and cal.Timestamp.

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[cavalle]

LGTM!