…ra/kibana into dashboard_align_attachment_to_api

* 'dashboard_align_attachment_to_api' of github.com:mbondyra/kibana: (45 commits)
  [OTel Tracing] HTTP instrumentation (elastic#258663)
  Replace deprecated EUI icons in files owned by @elastic/ml-ui (elastic#255624)
  [Codeowners] add missing codeowners for security_solution_api_integration tests (elastic#259223)
  [CI] fix bad imports that came from a merge-race (elastic#259383)
  Add `.claude/worktrees/` to `.gitignore` (elastic#259192)
  Improve unknown-key validation error message in @kbn/config-schema (elastic#258633)
  [ML] Update Security ML jobs to use entity analytics fields for host and user fields (elastic#255339)
  [Table sweep] Update table columns responsiveness in Index Management and Dashboards (elastic#259340)
  skip failing test suite (elastic#258790)
  skip failing test suite (elastic#259261)
  chore: util to clean cached images (elastic#259335)
  [Entity Store] Use last_seen for automated resolution watermark (elastic#258574)
  [One Workflow] Fix flaky alert trigger Scout test by removing order-dependent assertions (elastic#259299)
  Skip serverless Discover request counts tests for MKI (elastic#259333)
  [Security Solution] render header title in new document flyout in Security Solution and Discover (elastic#258166)
  [Agent Builder] register inference endpoint feature (elastic#259259)
  [Agent Builder] Skills Command Menu - Add descriptions and scope options to agent (elastic#258964)
  [Streams][Streamlang][API] Fully use meta({id}) to reuse schema partials in OAS output (elastic#259275)
  fix(files_example): add tableCaption to EuiInMemoryTable for a11y (elastic#258289)
  [Entity Store] Adding list endpoint with query filter (elastic#258320)
  ...

…lastic#258633)

resolves
[issue](elastic#249196)

## Summary

Improves the `@kbn/config-schema` `object.unknown` validation error
message from the unclear `"definition for this key is missing"` to a
more actionable `"Additional properties are not allowed ('<key>' was
unexpected)"`, following OpenAPI-style messaging.

### Problem
- When `schema.object()` with `unknowns: 'forbid'` (the default)
encounters an unexpected property, the error `"definition for this key
is missing"` is technically correct but not actionable.
- It does not tell callers that the failure is due to additional
properties being disallowed, nor does it name the offending key in the
message body.
- This is especially confusing in API workflows (e.g.
Dashboards-as-Code) where users copy GET response payloads into POST/PUT
requests and receive cryptic validation errors for response-only fields
like `meta`.

### Solution
- Updated `handleError` in `ObjectType` to return `"Additional
properties are not allowed ('<key>' was unexpected)"` for the
`object.unknown` Joi error code, using Joi's `child` context to include
the unexpected property name.
- Updated 46 test files across the repository that asserted the old
error string to match the new message format.
- All 893 affected Jest tests pass. `node scripts/check_changes.ts`
passes (lint + formatting).


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