feat: add reusable pre-commit workflow

[chris11-taylor-nttd]

Perform a lift-and-shift of pre-commit actions to a reusable workflow that can be called by other repos. Additionally, cleans up a tag reference on actions/checkout by replacing the tag with a SHA.

We'll need to do some work to update the downstreams to consume pre-commit in this way, but for the most part that change will roll out through the auto-update system on the skeleton.

[bryce-lynn-nttd]

The lift-and-shift shape is right, and the actions/checkout SHA pin closes my prior tag-pinning note from PR #88. One copy-paste bug worth fixing before this lands:

Blocking:

• name: Dependabot Auto-Merge on line 1 of reusable-pre-commit-checks.yml is a copy-paste from the dependabot-automerge workflow. The file's actual purpose is pre-commit, but every Actions UI in every consumer that uses this workflow will display "Dependabot Auto-Merge" as the workflow name. Once this propagates downstream via the skeleton auto-update flow, every converted repo's Actions tab will have the wrong label. One-line fix: change to name: Pre-Commit Checks (or similar).

Non-blocking:

• _placeholder input appears unnecessary. on: workflow_call: without an inputs: block is valid YAML — no placeholder needed. If there's a specific reason for scaffolding future inputs, worth a code comment explaining; otherwise drop the block.
• actions/checkout SHA ff7abcd0... doesn't map to any released tag in actions/checkout — it's a between-releases commit from 2025-08. This is the same SHA already used elsewhere in launch-workflows, so consistent with the repo, but worth knowing for a future bulk refresh to a tagged release (e.g., the SHA underlying v6).
• Cache pattern (restore-only) still appears here, but that's intentional now since PR #90 is the paired producer for those caches. Together the two PRs address the cache concern from PR #88.

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[chris11-taylor-nttd]

Fixed the workflow name, and dropped the placeholder input. Going to blame this on it being late on a Friday afternoon.

[ben-vaughan-nttd]

Codex PR Review

Note: This pull request review was generated by Codex.

Review Decision

APPROVE

High Findings

• (none)

Medium Findings

• (none)

Low Findings

• (none)

Nitpicks

• (none)

Previously Raised Findings Confirmed

• The prior reviewer’s blocking workflow-name finding and placeholder-input note appear resolved in the current revision. Codex is not claiming these as new findings.

Open Questions / Assumptions

• (none)

Required Workflow Status

• Required workflows overall: pass
• Failing required workflows: none
• Pending required workflows: none

Validation Notes

• Local checkout used: yes
• Existing PR comments/reviews checked: yes
• Existing findings confirmed but not claimed as new: prior workflow name and placeholder input findings were checked and appear resolved
• Net-new blocking findings from Codex: none
• Unresolved blocking findings from other reviewers: none observed in the current revision
• Required workflow checks evaluated: yes
• Required workflow failures found: none
• Required workflow failure investigation performed: not needed
• Instruction files discovered: none found
• Instruction files applied: workspace-level review guidance
• Instruction files skipped as out-of-scope: none
• User clarification requested for ambiguous scope: no
• Older duplicate Codex blocking review dismissed: no
• Checks/tests executed: pre-commit run --files .github/workflows/pull-request-precommit-checks.yml .github/workflows/reusable-pre-commit-checks.yml docs/reusable-pre-commit-checks.md

[bryce-lynn-nttd]

This supersedes my prior CHANGES_REQUESTED. Both findings cleanly addressed and empirically verified:

• Line 1 is now name: Pre-Commit Checks (was name: Dependabot Auto-Merge) — the copy-paste blocker is fixed.
• on: workflow_call: is now bare with no body — the unnecessary _placeholder input is dropped.

Two commits: fix: workflow name and fix: drop placeholder input. CI green. Approving.

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