da_build: add PDF/UA checker with severity classification and optional strict mode

[nonprofittechy]

This PR adds automated PDF accessibility validation to the da_build action using veraPDF (https://verapdf.org/), ensuring that PDFs in Docassemble repositories comply with the PDF/UA-1 (ISO 14289-1) standard.

For now, this defaults to being warnings only. In a future version of this action (probably about 30 days?) we will start failing repos that do not pass the PDF accessibility checks.

Key Features

• Smart Severity Levels: Categorizes accessibility rules to prioritize critical blockers while still surfacing advisory warnings:
  • Fail: Critical issues (e.g., untagged content, missing alt text, non-embedded fonts).
  • Warning: Advisory issues (e.g., missing metadata title, language tags).
  • Info/Suppressed: Technical details or rules that only matter in specific contexts (like non-flattened forms).
• Comprehensive Reporting:
  • GitHub Job Summary: Generates a detailed breakdown for every PDF, including rule descriptions and failure counts.
  • Annotations: Emits GitHub warning or error annotations directly in the action logs.

Configuration & Syntax

Add these optional inputs to the da_build step in your workflow:

 - uses: SuffolkLITLab/ALActions/da_build@main
   with:
     # Set to "error" to fail the build on accessibility failures (default is "warning")
     verapdf-validation-mode: "error"

     # Set to "true" to enforce tab-order and form-field annotation rules (default is "false")
     verapdf-strict: "true"

     # Set to "true" to skip the PDF check and veraPDF installation entirely
     skip-pdf-check: "true"

How to Adjust Strictness

• Default (Non-Strict): By default, rules related to tab-order (§7.18.3) and widget annotation structure (§7.18.4) are suppressed. Since many Docassemble interviews flatten form fields
  before they reach the user, these rules are often irrelevant.
• Strict Mode: Set verapdf-strict: "true" to treat these suppressed rules as regular failures.

How to Turn It Off

• Advisory Only: Keep the default verapdf-validation-mode: "warning". The check will run and report issues, but it will never fail your build.
• Complete Disable: Set skip-pdf-check: "true". This prevents the action from downloading/installing veraPDF and skips the scanning process entirely.

[Copilot]

Pull request overview

Adds automated PDF/UA-1 accessibility validation to the da_build composite GitHub Action using veraPDF, with rule severity classification and an optional strict mode to control how form/tab-order related rules are treated.

Changes:

• Add check_pdf_accessibility.py to run veraPDF, classify rule severities, emit annotations, and write a GitHub Step Summary report.
• Extend da_build/action.yml with new inputs (verapdf-validation-mode, verapdf-strict), install veraPDF, and run the checker.
• Document the new PDF accessibility behavior and inputs in README.md.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
da_build/check_pdf_accessibility.py	New checker script that runs veraPDF UA1 validation, buckets failures by severity, and outputs annotations + job summary.
da_build/action.yml	Adds inputs and new steps to install veraPDF and invoke the checker as part of da_build.
README.md	Documents PDF accessibility checking and the new action inputs.

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[nonprofittechy]

Sorry, I think this one is stale, just checking

[nonprofittechy]

Closing as superseded by #95. The PDF checker implementation is the same, while #95 is rebuilt on the newer da_build/main history and retains the uv migration and safe env-var input handling. It also uses the aligned pdf-validation-mode / pdf-strict inputs.