ci: add build verification workflow for PRs

[Copilot]

Adds dedicated build verification workflow to catch TypeScript compilation and lint failures early on all PRs.

Changes

• New workflow .github/workflows/build.yml:
  • Runs npm run lint and npm run build on push/PR to main
  • Tests across Node.js 18, 20, 22 matrix (matches engines: >=18.0.0)
  • Verifies build output exists (dist/cli.js)
  • Uses pinned action SHAs consistent with existing workflows

Making Required

To enforce on PRs, add status checks Build and Lint (Node 18/20/22) to main branch protection rules.

Original prompt

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This section details on the original issue you should resolve

<issue_title>[High Priority] Add build verification workflow for PRs</issue_title>
<issue_description>## Context
From CI/CD Pipeline Gap Assessment (Discussion #227)

Description

Extract and enforce build checks on all PRs to catch build failures early before merge.

Acceptance Criteria

• Create dedicated build verification workflow or extract from existing workflows
• Run TypeScript compilation (npm run build) on all PRs
• Make workflow required for PR merges
• Ensure compatibility check across Node versions if applicable

Estimated Effort

Approximately 1 hour

Related

• Discussion CI/CD Pipeline and Integration Tests - Gap Assessment #227</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [High Priority] Add build verification workflow for PRs #232

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[github-actions]

Test Coverage Report

Metric	Coverage	Covered/Total
Lines	77.19%	1300/1684
Statements	77.27%	1333/1725
Functions	77.17%	142/184
Branches	69.76%	450/645

Coverage Thresholds

The project has the following coverage thresholds configured:

• Lines: 38%
• Statements: 38%
• Functions: 35%
• Branches: 30%

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Coverage report generated by `npm run test:coverage`