Configuration: tomllib + flag override (config.py)

[GeoSpark]

Settings from TOML with CLI-flag override. See DESIGN.md §11, §12.

Scope

• config.py: load stac-validator-plus.toml (CWD or --config) via tomllib; Pydantic Settings with keys model (Bedrock ID), region, aws_profile, examine_runs, request_timeout, max_concurrent, cache_ttl (5m/1h), bundle_docs, wall_clock_budget, token_budget, enabled_plugins, enabled_checkers, reference_url_allowlist.
• Precedence: CLI flag > file > default. Default model = Sonnet (anthropic.claude-sonnet-5).

Depends on

#1

Test approach

TDD. Precedence resolution, missing file -> defaults, malformed TOML -> clear error.

Acceptance

• All keys load; flags override file.
• Sensible defaults (Sonnet, low examine_runs).