Avoid q2 sorted per-row global-code remap

[snissn]

Summary

• changes the q2 sorted grouped-distinct setup path to build dictionary-level local-code to global-rank maps instead of materializing per-row global-code arrays
• translates local codes to global ranks at sorted iterator boundaries for heap ordering and reduction
• keeps the existing q2 diagnostic field names for report compatibility, but the remap buckets now measure dictionary-level rank-map fill in this path

Scope / claim boundary

This is no-aggregate one-shot typed-column query setup work for q2 sorted grouped-distinct execution only. It is not metadata acceleration, and it should not be presented as ClickHouse superiority until current side-by-side evidence is regenerated.

The standard JSONBench full-prepared q2 path currently reports dense_group_count_distinct_used=true; that dense path remains separate and still uses its existing dense global-code/rank preparation. This PR is therefore still draft until we either attach a standard sorted-path acceptance artifact or explicitly decide to land it as a narrow sorted-path cleanup.

Evidence so far

Focused tests:

GOWORK=off go test ./TreeDB/collections -run 'TestTypedColumnQ2SortedGroupedDistinct|TestColumnPhysicalQueryDiagnosticsMerge' -count=1
GOWORK=off go test ./TreeDB/collections -run 'TestTypedColumnQ2' -count=1
GOWORK=off go test ./TreeDB/collections -count=1
git diff --check

All passed locally.

Exploratory 1M Bluesky sorted-path probe, using a temporary exported-API probe outside the repo:

• patched setup: 530.284 ms
• patched post-prepare: 178.488 ms
• patched residual run: about 186.562 ms
• patched wall total: 716.847 ms
• origin/main setup: 716.148 ms
• origin/main post-prepare: 242.269 ms
• origin/main residual run: about 203.111 ms
• origin/main wall total: 919.259 ms
• rows scanned: 1,000,000
• rows matched/reduced: 954,611
• result hash: 3ff6801dd9b080cd on both runs

Standard JSONBench q2 1M one-shot/no-metadata artifact against this branch:

• artifact: /tmp/jsonbench_q2_lazy_rank_1m_20260701_065655/report.json
• layout: column-store-full-prepared
• query mode: one_shot_end_to_end
• metadata mode: no_aggregate_metadata
• dense path: dense_group_count_distinct_used=true
• setup: 45.715 ms
• post-prepare: 20.480 ms
• run: 18.119 ms
• render/hash: 0.053 ms
• total: 63.887 ms
• rows scanned/matched/reduced: 1,000,000 / 954,611 / 954,611
• result hash: b63b8e1013c918fcda7c299ef64beb20c4988854cf0671a83803b6951d795860
• dense q2 split: group global rank 0.034 ms, distinct global rank 19.578 ms, part local rank 0.865 ms
• dense distinct split: plan 0.001 ms, collect refs 7.768 ms, build shards 11.809 ms, refs 627,646, global ranks 180,100

This standard artifact is useful q2 context/no-regression evidence, but it does not prove the sorted grouped-distinct change because the standard path is dense.

Acceptance evidence still required before merge

• standard sorted grouped-distinct q2 artifact, or an explicit decision to land this as a narrow sorted-path cleanup
• preserve rows scanned/matched/reduced and result hash on the affected path
• keep the standard dense q2 follow-up separate, targeting dense distinct rank/ref-build setup cost

Refs #3324
Refs #3070

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• Commit unit tests in branch codex/q2-lazy-global-rank-boundary-20260701

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