[MSE] Add resumable sorted merge joins on shared exchanges

[xiangfu0]

Adds opt-in resumable INNER and LEFT sorted merge joins. Explicit sorted strategy requires the broker capability gate, plans complete ASC NULLS LAST sender sorts and distinct k-way merge receives, and preserves explicit or inferred colocation through the Sort. Unsupported clusters fail logical planning; V2 keeps its explicit rejection.

Duplicate-key buffers and output blocks are bounded. Null/LONG/residual semantics remain intact. Early termination, exhausted inputs and BREAK drain terminal mailbox blocks so late errors and upstream statistics survive. The new leaf dependency's streaming instance-plan regression is preserved, and shared window fixtures have no incidental changes. The native diff contains 20 join feature files.

Validation: 716 unique applicable JDK 25 cases, including 35 sorted join tests, eight mailbox terminal regressions, three H2 comparisons, full following/RANGE window coverage and 57 core streaming combine cases; repeated classes are counted once and the two unchanged broker gate cases are explicitly reused. No failures/errors/skips or warnings on added lines. Mandatory affected formatting, license and checkstyle checks pass.

This PR remains stacked on #19712. Hosted CI at its final remote head and reviewer/base decisions remain open; local tests do not claim remote green CI. The cached capability gate is not an atomic downgrade guarantee, and #19395's stalled-sender memory followup remains deferred.

Final stacked head: b82686e30f759d1610e2021967c3cef7fd3234cd; dependency head: 88ef14a0fd97415f58c1aefc15c33a6620c759d6. Existing base names remain unchanged; the new dependency heads await root's guarded second publication.

The inherited fixture followup independently passes all 593 ResourceBasedQueryPlansTest cases on this exact source tree with compiler warnings/deprecations enabled, zero failures/errors/skips and all four planner formatting/license/style goals passing. Its native feature patch is byte-identical to the preceding published stack; only core owns the 124 corrected window-input fetch expectations. These local results do not establish hosted CI status.

The existing stack base is retained. Full unit/integration PR workflows are filtered to master; no complete hosted CI result exists for this child at its current stack base. After the prerequisite PRs land, the agreed base update and exact-head CI are still required. No merge, automatic merge, CI suppression or master integration was performed.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 83.72881% with 48 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (xiangfu0/codex1/sorted-exchange-leaf@88ef14a). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
...uery/runtime/operator/SortedMergeJoinOperator.java	88.35%	18 Missing and 11 partials ⚠️
...not/query/runtime/operator/MultiStageOperator.java	14.28%	6 Missing ⚠️
...ite/rel/rules/PinotJoinExchangeNodeInsertRule.java	77.77%	0 Missing and 4 partials ⚠️
...e/pinot/query/runtime/InStageStatsTreeBuilder.java	20.00%	3 Missing and 1 partial ⚠️
.../apache/pinot/query/planner/plannode/JoinNode.java	40.00%	2 Missing and 1 partial ⚠️
.../query/planner/logical/RelToPlanNodeConverter.java	50.00%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@                           Coverage Diff                           @@
##             xiangfu0/codex1/sorted-exchange-leaf   #19713   +/-   ##
=======================================================================
  Coverage                                        ?   68.32%           
  Complexity                                      ?     1450           
=======================================================================
  Files                                           ?     3529           
  Lines                                           ?   230118           
  Branches                                        ?    36594           
=======================================================================
  Hits                                            ?   157226           
  Misses                                          ?    60559           
  Partials                                        ?    12333           

Flag	Coverage Δ
integration	100.00% <ø> (?)
integration1	100.00% <ø> (?)
integration2	0.00% <ø> (?)
java-25	68.32% <83.72%> (?)
lane-a	100.00% <ø> (?)
lane-b	0.00% <ø> (?)
temurin	68.32% <83.72%> (?)
unittests	68.32% <83.72%> (?)
unittests1	58.41% <83.72%> (?)
unittests2	39.67% <1.35%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[xiangfu0]

CI follow-up at c5852643 adds six exact stacked-base pull_request branch filters (+6/-0). Feature code/tests and existing master/push, path, permission and job rules are preserved.

Current-head checks finished with 13/14 passing. Integration Set 2 failed again after one failed-job-only rerun: SameTableNameMultiClusterIntegrationTest hit a broker HTTP BindException during setup, before query assertions (latest failed job). The first attempt failed at a different fixture listener (Netty QueryServer). All 11 directly implicated fixture/startup/POM files are identical to the frozen base; the actual conflicting socket remains unknown.

This PR still has an open CI gate. A separate baseline fixture startup repair and validation remain necessary; the six-line workflow change is preserved. Maintainer review remains pending.