DOC-6827 Add Lettuce probabilistic data type examples and rundown page

[andy-stark-redis]

Summary

Adds Lettuce (Java) coverage for the probabilistic data types, in two parts.
Documentation only — 15 files, all additions.

Examples

Staged Lettuce async + reactive doctests under
local_examples/<set>/lettuce-async|lettuce-reactive/:

Set	Data-type page
bf_tutorial	Bloom filter
cuckoo_tutorial	Cuckoo filter
cms_tutorial	Count-min sketch
topk_tutorial	Top-K
tdigest_tutorial	t-digest
hll_tutorial	HyperLogLog
home_prob_dts	combined rundown / landing

The per-type data-type pages embed clients-example without a lang_filter, so the
new Java-Async and Java-Reactive tabs appear automatically once the example
pipeline regenerates examples.json — no edits to those pages are needed, and none
are in this PR. Confirmed in a local build: all six probabilistic data-type pages
pick up both tabs.

Rundown page

New content/develop/clients/lettuce/prob.md, adapted from the Jedis page, with
lang_filter="Java-Async,Java-Reactive".

Requirements

The probabilistic commands need Lettuce 7.7.0 or later (released 2026-08-18), which
is the first release carrying Bloom, Cuckoo, CMS, t-digest, Top-K and HLL support. It is
still the current release.

In line with the Jedis, redis-py, Go and Node.js probabilistic pages — none of which
state a client version requirement — prob.md carries no version banner.

Verification

Not inspection-only; the examples were compiled and run:

• All 14 files compile against lettuce-core 7.7.0.RELEASE.
• All 14 pass against a live Redis 8.10.1, through the repo's own harness
  (./run.sh <set> lettuce-async lettuce-reactive) as well as directly.
• 140 of 140 >>> expected-output comments were mechanically diffed against
  observed stdout, rather than spot-checked. All match.
• Top-K eviction order, the one non-obvious output, was confirmed stable across
  repeated fresh runs.
• Hugo builds clean, with no new warnings and none naming a probabilistic set.

Re-verified after merging main on 2026-09-10, against a newer server (8.10.1) than
the examples were originally written and checked against.

Notes for review

Two things worth a look, both of which only surfaced once the examples could actually
be executed:

• t-digest values are double, not String. tdigestAdd, tdigestRank and
  tdigestCDF take a double value parameter, so the numeric arguments are unquoted.
• The reactive Top-K tabs show a Value wrapper, and the async ones show null.
  This asymmetry is deliberate in Lettuce, not an inconsistency in the docs: reactive
  returns Flux<Value<String>> while async returns RedisFuture<List<String>>,
  because a Flux cannot emit null whereas a List can hold it. So the reactive tab
  prints Value.empty / Value[handlebars] where the async tab prints null /
  handlebars.

Not covered

tdigestByRevRank, tdigestRevRank, tdigestTrimmedMean, tdigestInfo,
cmsInitByDim and cmsMerge exist in 7.7.0 but are not exercised by these examples —
possible future coverage, not a gap in what is documented here.

---

Note

Low Risk
Documentation and example/test assets only; any harness dependency bump mainly affects CI compile of Lettuce examples, not production runtime.

Overview
Adds Lettuce client documentation for Redis probabilistic data types via new content/develop/clients/lettuce/prob.md, mirroring other clients’ rundown pages and wiring clients-example snippets for Java-Async and Java-Reactive (home_prob_dts steps: Bloom, Cuckoo, HyperLogLog, CMS, t-digest, Top-K).

Introduces 14 doctest-style examples under local_examples/ (async + reactive for bf_tutorial, cuckoo_tutorial, cms_tutorial, hll_tutorial, tdigest_tutorial, topk_tutorial, and the combined home_prob_dts set), so existing probabilistic data-type pages can pick up Lettuce tabs once examples.json is regenerated.

Per the PR notes, the example harness is intended to use lettuce-core 7.7.0+ for these probabilistic APIs (that pin may land with or alongside this docs work).

^{Reviewed by Cursor Bugbot for commit 4af834c. Bugbot is set up for automated code reviews on this repo. Configure here.}

[github-actions]

DOC-6827

[github-actions]

Staging links:
https://redis.io/docs/staging/DOC-6827-prepare-lettuce-probabilistic-data-type-docs/develop/clients/lettuce/prob/

[github-actions]

🧠 Redis Memory

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Memory updated at 4af834c

[dwdougherty]

LGTM.