feat(cli): DO NOT MERGE emit telemetry for the validate action

[iankhou]

DO NOT MERGE until we enable the VALIDATE event on the Telemetry backend.

The cdk validate action (unstable) runs offline and online validation but currently emits no telemetry. This adds a VALIDATE telemetry event so we can measure, at minimum, that the validation engine ran (start time, duration, success/failure), and whether offline validation caught errors that would have failed a deployment.

Not included

cdk validate --watch does not emit VALIDATE events.

We must enable our Telemetry backend to accept VALIDATE events.

Checklist

• Unit tests added/updated (count-validation-results.test.ts, cli-io-host.test.ts, validate.test.ts + io-snapshots)
• Integration tests: n/a — no new resource types or cross-service interactions
• No manual edits to generated files

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

[github-actions]

Dependency Review

✅ No vulnerabilities or license issues or OpenSSF Scorecard issues found.

Scanned Files

None

[codecov-commenter]

Codecov Report

❌ Patch coverage is 93.02326% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.01%. Comparing base (88f6ad1) to head (05059e6).
⚠️ Report is 19 commits behind head on main.

Files with missing lines	Patch %	Lines
packages/aws-cdk/lib/cli/io-host/cli-io-host.ts	33.33%	2 Missing ⚠️
packages/aws-cdk/lib/cli/cdk-toolkit.ts	95.83%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1864      +/-   ##
==========================================
+ Coverage   90.31%   91.01%   +0.69%     
==========================================
  Files          80       80              
  Lines       12159    12297     +138     
  Branches     1725     1768      +43     
==========================================
+ Hits        10982    11192     +210     
+ Misses       1143     1068      -75     
- Partials       34       37       +3     

Flag	Coverage Δ
suite.unit	91.01% <93.02%> (+0.69%)	⬆️

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[Copilot]

Pull request overview

Adds telemetry for non-watch cdk validate runs, including duration, errors, and validation-result counters.

Changes:

• Introduces the VALIDATE telemetry event and span.
• Counts offline and online validation outcomes.
• Adds unit tests and updated I/O snapshots.

Reviewed changes

Copilot reviewed 18 out of 18 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
packages/aws-cdk/lib/cli/cdk-toolkit.ts	Wraps validation in a telemetry span.
packages/aws-cdk/lib/cli/io-host/cli-io-host.ts	Converts validation messages into telemetry events.
packages/aws-cdk/lib/cli/telemetry/messages.ts	Defines validation span messages.
packages/aws-cdk/lib/cli/telemetry/schema.ts	Adds the VALIDATE event type.
packages/aws-cdk/lib/api-private.ts	Exposes validation counter utilities internally.
packages/@aws-cdk/toolkit-lib/lib/toolkit/toolkit.ts	Uses the shared online-validation plugin name.
packages/@aws-cdk/toolkit-lib/lib/toolkit/private/validation-report.ts	Defines the online-validation plugin constant.
packages/@aws-cdk/toolkit-lib/lib/toolkit/private/count-validation-results.ts	Calculates validation telemetry counters.
packages/@aws-cdk/toolkit-lib/test/toolkit/count-validation-results.test.ts	Tests validation counter calculation.
packages/aws-cdk/test/cli/io-host/cli-io-host.test.ts	Tests VALIDATE event emission.
packages/aws-cdk/test/commands/validate.test.ts	Tests validation span outcomes.
packages/aws-cdk/test/commands/__io_snapshots__/validate/with_violations_reports_multiple_violations_from_multiple_plugins.ndjson	Updates validation output snapshot.
packages/aws-cdk/test/commands/__io_snapshots__/validate/with_violations_reports_failure_when_validation_report_has_violations.ndjson	Updates failure output snapshot.
packages/aws-cdk/test/commands/__io_snapshots__/validate/telemetry_ends_the_VALIDATE_span_with_the_error_name_when_the_engine_crashes.ndjson	Captures crash telemetry output.
packages/aws-cdk/test/commands/__io_snapshots__/validate/telemetry_emits_a_VALIDATE_span_end_message_with_offline_violation_counters.ndjson	Captures violation-counter output.
packages/aws-cdk/test/commands/__io_snapshots__/validate/telemetry_emits_a_VALIDATE_span_end_message_even_when_no_violations_are_found.ndjson	Captures successful validation telemetry.
packages/aws-cdk/test/commands/__io_snapshots__/validate/stack_selection_validates_a_single_selected_stack.ndjson	Updates stack-selection output.
packages/aws-cdk/test/commands/__io_snapshots__/validate/no_violations_reports_success_when_no_validation_report_exists.ndjson	Updates no-report output.

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