Fix pdf_form_filler tests to mock ANTHROPIC_API_KEY

[Ammar-Bin-Yasir]

Seed a dummy ANTHROPIC_API_KEY via monkeypatch.setenv so the mocked LLM tests run offline without requiring a real key.

Fixes #387

Description

Type of Change

• New Skill — new registry bundle under skills/
• Skill Upgrade — changes to an existing skill under skills/
• Bug Fix — incorrect runtime or framework behavior
• Documentation — docs, README, CONTRIBUTING only
• Framework Feature — skillware/core/ loader, env, adapters
• CLI — skillware/cli.py, docs/usage/cli.md
• Examples — examples/*.py, agent loops, examples/README.md
• Packaging — PyPI wheel, pyproject.toml, MANIFEST.in
• RFC / meta — templates, labels, CI, or large design doc

Checklist (all PRs)

• Linked GitHub issue (Fixes #… or Refs #…)
• Scope matches the issue — no unrelated refactors
• python -m black --check . and flake8 pass locally (or CI-equivalent subset)
• pytest skills/ and pytest tests/ pass locally when relevant
• CHANGELOG.md updated under [Unreleased] when user-visible behavior changes
• examples/README.md updated if this PR adds, renames, or removes a runnable script
• Ran pytest tests/test_registry_docs.py when skills, examples index, or agent-loops matrix changed
• Ran pytest tests/test_skill_docs.py when catalog Usage Examples or provider snippets changed

New or updated skill

Skip unless this PR adds or changes files under skills/.

Bundle and metadata

• Skill at skills/<category>/<skill_name>/ (from templates/python_skill/ or equivalent)
• manifest.yaml: name (full ID), version, description, parameters, constitution, real issuer
• Optional: short_description, issuer.github, issuer.org, requirements, env_vars

Effect, Directive, Assurance

• Deterministic skill.py (Effect; no ad-hoc LLM-generated execution paths)
• instructions.md (Directive) explains when and how to use the skill
• card.json (Presentation) issuer matches manifest when present
• test_skill.py (Assurance) covers execution and schema expectations
• SkillLoader.load_skill("<category>/<skill_name>") succeeds (or deps documented)

Documentation and catalog

• docs/skills/<category>/<skill_name>.md, category hub row, row in docs/skills/README.md, and docs/sitemap.md
• Usage Examples for Gemini, Claude, OpenAI, DeepSeek, Ollama per skill usage template

Constitution and safety (skills only)

Related Issues

[Ammar-Bin-Yasir]

This only touches the two test files (adding monkeypatch.setenv for the mocked LLM tests), so I left the "New or updated skill" section unchecked since no bundle/manifest/docs changed. Let me know if you'd like anything else checked.

[rosspeili]

LGTM @Ammar-Bin-Yasir, merged.