refactor(metrics): fold single-consumer timer helper into registry

[DavidHLP]

Summary

Implements the scoped C1 architecture recommendation from the supplied 2026-09-19 review: move the single-consumer timer primitives into RedisProCacheMetricsRegistry while preserving the metrics contract.

Scope

• migrate the primitive behavior contract into the registry test surface;
• inline the primitives and remove the redundant helper/test;
• preserve metric names, tags, descriptions, null-safe paths, timing/finally behavior, exception propagation, and put/evict counter semantics;
• add explicit recordEvict body-failure coverage for timer and operation-counter finalization;
• update all tracked source/test references and stale six-meter wording after the helper deletion;
• assert all seven meters (3 timers + 4 counters) by name, cache tag, and description;
• leave the reviewed C2-C4 candidates unchanged because current evidence shows no additional seam pressure.

Tracking

Closes #25
Closes #26
Closes #28
Closes #27

Verification

Final PR head: f245ac86bdd74d4609cbfb97e2ae83e90b010fbd.

• Focused registry test: 35 passed, including all seven meter metadata assertions and the recordEvict body-failure path.
• Remote Java 21 unit gate: 718 passed, 0 failures/errors/skips.
• Remote Checkstyle: 0 violations.
• Repository test-name and docs-contract guards: passed.
• Packaged external consumer: EXTERNAL_CONSUMER_OK, RM-010 PASS.
• Full GitHub PR pipeline for the final head: all 10 reported checks passed, including Java 21 Build & Verify, unit tests, package, JMH, docs, Checkstyle, quality, and ci-ok.
• Repository-wide tracked-source scan: no RedisProCacheTimers references remain; stale six-meter wording removed from the changed source/test surfaces.
• git diff --check: passed.

The remote consumer gate used the installed Java 21 path explicitly because the script's default path is not present on remote-dev; no project source or configuration was changed for that environment detail.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-19T05:43:12.630260Z	f245ac8	New commits

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