CI: Add CTest for ApplySearch Threading

[xsscx]

PR Summary

#2346

Checklist

• Signed all Commits in PR
• Built locally according to docs/build.md
• Followed the guidelines in Contributing document
• Ran relevant CTest/profile tests from docs/ctest.md
• Updated documentation for user-visible behavior changes
• Ran sanitizer coverage for memory-safety or parser changes
• Added or updated regression coverage for behavior changes
• Attached a base...HEAD contract matrix for cross-cutting changes:
  producer, consumer, build/runtime behavior, platform/toolchain boundary,
  CI trigger, dependency owner, and local evidence
• Reviewed active and suppressed automated findings from review threads and summaries
• For Python package changes, followed docs/python-packaging-release.md for PR and merge requirements
• Did not change maintainer-owned workflow, CTest, CPack, sanitizer, release, or security infrastructure unless requested by an iccDEV maintainer
• New source files include the ICC copyright and BSD 3-Clause license header
• Code style matches nearby code: 2-space indent, K&R braces, m_ members

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[xsscx]

PR Author Notes

2026-09-03 18:10:29 UTC

This PR started in #2363 but Stacked PR was not helping with the Copilot Code Review Process.

• Started smaller, beginning with fix: add threaded ApplySearch workers #2373
  • Rebased this PR on that Commit with less Content
• Additional PRs to add CTest & Doc Updates

[Copilot]

🟡 Changes recommended

The new threads-debugcalc regression currently doesn’t assert the expected diagnostic (so it can pass for unrelated failures), and the threaded fixture generation uses a hard-coded repeat count that is unnecessarily fragile.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

This PR strengthens CI regression coverage for iccApplySearch threading by expanding the existing iccdev.applysearch-cli-args CTest to validate deterministic output across multiple -threads settings and to pin several malformed thread-count argument cases.

Changes:

• Generate a >1024-row derived input fixture to ensure the threaded bulk path is exercised, then compare output across -threads 0/1/2/4/8.
• Add negative tests for invalid -threads values and invalid flag usage combinations (including -debugcalc + non-1 threads).
• Document the expanded iccdev.applysearch-cli-args coverage in docs/ctest.md.

File summaries

File	Description
docs/ctest.md	Documents the expanded iccdev.applysearch-cli-args threading and argument-surface coverage.
.github/scripts/iccdev-applysearch-cli-args-regression.sh	Extends the regression script to exercise threaded batch apply, validate deterministic output across thread counts, and pin additional -threads rejection cases.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 2
• Review effort level: Lite

[colourbill-ctrl]

Reviewed at f01b651d. CI skipped every build lane on this script+docs change, so the execution evidence is local: ctest -R iccdev.applysearch-cli-args passes against master 3e2224d2 in 1.8s.

The fixture is not vacuous: 1,040 rows clears the 1,024 bulk threshold, so pixelsPerThread drops to 128 and every requested worker dispatches. Measured on that exact fixture, -threads 1/2/4/8: 0.28s / 0.21s / 0.10s / 0.07s wall, CPU rising 0.28s to 0.52s, output byte-identical throughout. Rejection cases match the tool: bare -threads, -threads 8 alone, -1, 257 (with the expected 0..256 text), nope, and -debugcalc with workers all exit non-zero.

Approving.