ci(nightly): set fail-fast: false on the build matrix

[rgsl888prabhu]

Summary

Make the two matrix entries in .github/workflows/nightly.yaml independent so a missing release-branch ref no longer cancels the working main-branch nightly.

Why this matters now: the matrix bumped to release/26.06 in #1091 on 2026-04-14, but release/26.06 has not been cut from main yet. Every nightly since has failed — the release entry 404s at the gh api .../branches/release/26.06 lookup, the matrix's default fail-fast: true cancels the sibling main entry, and the wrapper job reports failure even though the main dispatch would have succeeded on its own.

Fix: add fail-fast: false so each cuopt_branch dispatch runs independently.

strategy:
  fail-fast: false       # ← added
  matrix:
    cuopt_branch:
      - "main"
      - "release/26.06"

The release entry will still go red until release/26.06 is actually cut (or the line is reverted to a release branch that exists), but it no longer drags main with it.

Test plan

• Watch the next scheduled nightly — main matrix entry should dispatch and complete independent of the release/26.06 entry's outcome.
• Manual dispatch via Run workflow from Actions UI to verify both entries run to completion (or independent failure) before waiting for the cron.

🤖 Generated with Claude Code

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ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 9fd1763 and 073531e.

📒 Files selected for processing (1)

• .github/workflows/nightly.yaml

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📝 Walkthrough

Walkthrough

The nightly GitHub Actions workflow is updated to add fail-fast: false to the job strategy matrix, ensuring that when one cuopt_branch variant fails, the remaining matrix entries continue executing instead of being cancelled immediately.

Changes

Nightly Workflow Matrix Strategy

Layer / File(s)	Summary
Matrix Strategy Configuration .github/workflows/nightly.yaml	Job strategy block adds fail-fast: false to the trigger-nightly-builds-and-tests matrix, ensuring all cuopt_branch variants run to completion regardless of individual failures.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: adding fail-fast: false to the build matrix in the nightly CI workflow.
Description check	✅ Passed	The description is detailed and directly related to the changeset, explaining the problem with the matrix failure cascading and how the fix resolves it.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[rgsl888prabhu]

/merge