#342 feat(gov): add Government Index search filters

firecrawl gov gets --jurisdiction, --court, --court-type, --cites and --domain. Set filters go out as query parameters on GET /v2/search/gov; a search without filters sends the same URL as before.

• Values are checked before the request: court types against the allowed list, the jurisdiction shape, and non-empty court, citation and domain values.
• When the API refuses a request, for example an unknown court id, the CLI prints the API's message instead of the HTTP status.
• The README, --help and the bundled skills document the flags and the coverage caveat.

Bumps the version to 1.26.20, skipping the 1.26.19 that #343 claims. Merge once the API filters in firecrawl/firecrawl#5338 are deployed; merging publishes 1.26.20.

Show me

$ firecrawl gov "qualified immunity excessive force" --court ca9
  -> GET /v2/search/gov?query=...&court=ca9&integration=cli

$ firecrawl gov "zoning" --court-type supreme
error: option '--court-type <type>' argument 'supreme' is invalid. Allowed choices are federal-supreme, ...   (no request sent)

$ firecrawl gov "zoning" --court zz9
Error: invalid 'court' parameter: pass a CourtListener court id such as scotus, ca9, nh or calctapp

Validation

• pnpm run type-check, pnpm run format:check, pnpm run build and pnpm test pass.
• Against a local API build: each flag reached the API with the expected parameters, invalid values sent no request, and an unknown court id printed the API's message.