fix(xerrors): keep outer fields when rendering collected errors

[Kybxd]

Problem

Errors produced by a Collector lose the fields attached by enclosing WrapKV layers when rendered via Error(). Since Desc.Stringify picks the message template by the Module field, losing it makes the default template render instead of the module-specific one.

The practical impact: confgen load errors lose Workbook / Worksheet / DataCellPos / DataCell, so there is no hint about which cell to fix. A refer check failure looks like this:

error[E2002]: field value not in referred space
Reason: value "100033333" not in referred space "ItemConf.ID"
Help: guarantee value "100033333" was configured in referred space "ItemConf.ID" ahead

The fields are all correctly attached along the chain (tableParser.Parse adds CellDebugKV, parseMessageFromOneImporter adds Module/BookName/SheetName) — they are only dropped at render time.

This is easy to hit from a downstream checker built on load, which reports issues via err.Error().

Root causes

Two distinct bugs, each affecting a different sheet layout:

1. collected did not implement fieldsRenderer.

withMessage.Error() on a fields-only wrapper delegates through base.renderWithFields, which requires the cause to implement fieldsRenderer. collected only implemented Error/Unwrap/Format, so rendering fell back to c.error.Error() — i.e. joinError.Error() == renderWithFields(nil) — discarding every outer field. This affects single-importer sheets.

2. Collector.Collect only remembered the outermost withMessage layer.

Wrapper chains commonly spread fields across several layers: confgen adds Module in sheetParser.Parse's defer, then BookName/SheetName in parseMessageFromOneImporter, and for multiple importers ParseMessage's Group.Go adds yet another layer carrying only book/sheet names and no Module. Keeping just err.(*withMessage) therefore dropped Module, so multi-importer sheets (merger / scatter) still rendered the default template even after fix 1.

Fix

• Implement fieldsRenderer on collected, forwarding outerFields to the inner error.
• Add outerFieldsUntil, which walks every wrapper layer between the error and the collected marker and merges their fields (inner layers win), replacing the outermost-layer-only logic in Collect.

Result

Both single- and multi-importer sheets now render the module-specific template:

error[E2002]: field value not in referred space
Workbook: Activity_ActivityCenter.xlsx (Primary: Activity.xlsx)
Worksheet: SectionConf
DataCellPos: S218
DataCell: 100033333
Reason: value "100033333" not in referred space "ItemConf.ID"
Help: guarantee value "100033333" was configured in referred space "ItemConf.ID" ahead

For a merger sheet it additionally pinpoints which merged workbook the bad cell lives in, which the primary book name alone cannot express.

Tests

Two regression tests are added, mirroring the real confgen chains (single-importer and multi-importer). Each was verified to fail independently when only its corresponding fix is reverted:

• revert fix 1 → only TestCollected_ErrorPropagatesOuterFields fails
• revert fix 2 → only TestCollected_ReCollectPreservesAllWrapperFields fails

go test ./... (including test/functest), go vet and golangci-lint run all pass. Verified end to end against a real spreadsheet tree, where the reported cell SectionConf!S218 was confirmed to hold the offending value.

[github-actions]

The latest Buf updates on your PR. Results from workflow Buf CI / buf (pull_request).

Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Aug 12, 2026, 9:36 AM

[codecov]

Codecov Report

❌ Patch coverage is 92.85714% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 75.65%. Comparing base (7bc5b61) to head (5f434a3).

Files with missing lines	Patch %	Lines
internal/x/xerrors/collector.go	92.85%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #449      +/-   ##
==========================================
+ Coverage   75.63%   75.65%   +0.02%     
==========================================
  Files          88       88              
  Lines        9531     9543      +12     
==========================================
+ Hits         7209     7220      +11     
- Misses       1747     1748       +1     
  Partials      575      575              

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