Add telemetry error classification guardrails

[prathamesh-db]

Description

Telemetry-visible JDBC errors need two things to remain useful downstream: a stable DatabricksDriverErrorCode and an explicit driver/server/user classification. Missing either can leave the telemetry dashboard and automation taxonomy out of sync.

This PR adds lightweight repository guardrails for future error changes:

• CLAUDE.md tells contributors to reuse or add an enum-backed code, verify the emitted name and numeric code in tests, and record the classification.
• The pull-request template asks authors to confirm those steps or request maintainer help when they cannot access the classification system.

The classification source is maintainer-owned and is not available to public-repository CI. The checks therefore remain review-based instead of adding CI that could validate only a PR checkbox, not the underlying classification.

NO_CHANGELOG=true

Testing

Documentation and review-routing changes only; this PR does not change driver build or runtime behavior.

• Verified the exact error-code enum path referenced by the guidance.
• Verified the pull-request checklist covers both error-code and classification updates.
• git diff --check passes.

Telemetry Errors

• Not applicable — this PR does not add or change a telemetry-visible error.
• Applicable — the error uses DatabricksDriverErrorCode where appropriate, and any new code is uniquely numbered and tested.
• Applicable — its driver/server/user classification is linked, or maintainer help is requested because the author cannot access the classification.

Additional Notes to the Reviewer

This is intentionally a lightweight contributor and reviewer guardrail. It does not duplicate the maintainer-owned taxonomy in the public repository or automatically classify existing errors.

[samikshya-db]

When you are raising a fix, see if this is useful - we can modify the claude.md as required. Approving this for now.

[prathamesh-db]

/merge

[prathamesh-db]

/trigger all