RUBY-3898 Remove dead cursor-pinning block, fix cursor id for OP_MSG

[comandeo-mongo]

Operation::Result#has_cursor_id? checked replies.last.respond_to?(:cursor_id), which is only true for the legacy Protocol::Reply. Every modern reply is a Protocol::Msg, so the predicate was always false. Two call sites depended on it:

• The load-balanced cursor pin/unpin block in executable.rb never executed. LB cursors already retain their connection via explicit ownership (Cursor holds @connection since RUBY-3616, released by Cursor#check_in_connection), so the block was a redundant guard.
• The OpenTelemetry db.mongodb.cursor_id attribute on find/aggregate spans was gated on the dead predicate and therefore never recorded (the request-message path only covers getMore/killCursors).

Changes

• lib/mongo/operation/shared/executable.rb — removed the dead LB cursor pin/unpin block. Transaction pinning, snapshot handling, and process_result are unchanged.
• lib/mongo/operation/result.rb — removed has_cursor_id?; made base cursor_id read the id from the OP_MSG cursor subdocument (returning 0 when absent), so it is safe to call on any command result.
• lib/mongo/tracing/open_telemetry/command_tracer.rb — gate process_cursor_context on cursor_id.positive?. Find/aggregate spans now record db.mongodb.cursor_id.
• Specs — replaced the #has_cursor_id? coverage in result_spec.rb with OP_MSG #cursor_id cases; updated tracer spec doubles to stub cursor_id instead of the removed predicate.

Test plan

• bundle exec rubocop on all changed files — no offenses
• bundle exec rspec spec/mongo/operation/result_spec.rb spec/mongo/tracing/open_telemetry/command_tracer_spec.rb — 142 examples, 0 failures
• bundle exec rspec spec/mongo/cursor_spec.rb spec/integration/cursor_pinning_spec.rb — 46 examples, 0 failures, 5 pending (LB-only cases, skipped on local replica set)
• LB cursor_pinning_spec cases run in the Evergreen load-balanced variant (connection-retention regression guard)

RUBY-3898

[Copilot]

Pull request overview

This PR fixes cursor ID handling for OP_MSG command replies by making Operation::Result#cursor_id work across modern responses, removing an always-false predicate, and ensuring OpenTelemetry spans can record db.mongodb.cursor_id for find/aggregate results.

Changes:

• Remove the dead Operation::Result#has_cursor_id? predicate and update cursor_id to read from the OP_MSG cursor.id subdocument (defaulting to 0).
• Remove the non-functional load-balanced cursor pin/unpin block guarded by the dead predicate.
• Update OpenTelemetry command tracing and specs to gate cursor context on cursor_id.positive? and stub cursor_id in doubles.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
lib/mongo/operation/shared/executable.rb	Removes unreachable LB cursor pin/unpin logic guarded by the removed predicate.
lib/mongo/operation/result.rb	Removes has_cursor_id?; makes cursor_id work for OP_MSG cursor.id replies with a safe default.
lib/mongo/tracing/open_telemetry/command_tracer.rb	Changes cursor context gating to rely on cursor_id.positive? to enable recording cursor IDs on command spans.
spec/mongo/operation/result_spec.rb	Replaces has_cursor_id? tests with OP_MSG cursor-id extraction cases.
spec/mongo/tracing/open_telemetry/command_tracer_spec.rb	Updates doubles to stub cursor_id (removes predicate stubbing) and keeps span attribute expectations.

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